Dimensionally stable fast etching glasses

ABSTRACT

Substantially alkali free glasses are disclosed with can be used to produce substrates for flat panel display devices, e.g., active-matrix liquid crystal displays (AMLCDs). The glasses have high annealing temperatures and etch rates. Methods for producing substantially alkali free glasses using a downdraw process (e.g., a fusion process) are also disclosed.

This application claims the benefit of priority to U.S. ProvisionalApplication No. 62/151,741 filed on Apr. 23, 2015 and U.S. ProvisionalApplication No. 62/073,938 filed on Oct. 31, 2014 the content of eachare incorporated herein in its entirety.

TECHNICAL FIELD

Embodiments of the present disclosure relate to display glass. Moreparticularly, embodiments of the present disclosure relate to displayglass for active matrix liquid crystal displays.

BACKGROUND

The production of liquid crystal displays, for example, active matrixliquid crystal display devices (AMLCDs) is complex, and the propertiesof the substrate glass are important. First and foremost, the glasssubstrates used in the production of AMLCD devices need to have theirphysical dimensions tightly controlled. The downdraw sheet drawingprocesses and, in particular, the fusion process described in U.S. Pat.Nos. 3,338,696 and 3,682,609, both to Dockery, are capable of producingglass sheets that can be used as substrates without requiring costlypost-forming finishing operations such as lapping and polishing.Unfortunately, the fusion process places rather severe restrictions onthe glass properties, which require relatively high liquidusviscosities.

In the liquid crystal display field, thin film transistors (TFTs) basedon poly-crystalline silicon are preferred because of their ability totransport electrons more effectively. Poly-crystalline based silicontransistors (p-Si) are characterized as having a higher mobility thanthose based on amorphous-silicon based transistors (a-Si). This allowsthe manufacture of smaller and faster transistors, which ultimatelyproduces brighter and faster displays.

One problem with p-Si based transistors is that their manufacturerequires higher process temperatures than those employed in themanufacture of a-Si transistors. These temperatures range from 450° C.to 600° C. compared to the 350° C. peak temperatures employed in themanufacture of a-Si transistors. At these temperatures, most AMLCD glasssubstrates undergo a process known as compaction. Compaction, alsoreferred to as thermal stability or dimensional change, is anirreversible dimensional change (shrinkage) in the glass substrate dueto changes in the glass fictive temperature. “Fictive temperature” is aconcept used to indicate the structural state of a glass. Glass that iscooled quickly from a high temperature is said to have a higher fictivetemperature because of the “frozen in” higher temperature structure.Glass that is cooled more slowly, or that is annealed by holding for atime near its annealing point, is said to have a lower fictivetemperature.

The magnitude of compaction depends both on the process by which a glassis made and the viscoelastic properties of the glass. In the floatprocess for producing sheet products from glass, the glass sheet iscooled relatively slowly from the melt and, thus, “freezes in” acomparatively low temperature structure into the glass. The fusionprocess, by contrast, results in very rapid quenching of the glass sheetfrom the melt, and freezes in a comparatively high temperaturestructure. As a result, a glass produced by the float process mayundergo less compaction when compared to glass produced by the fusionprocess, since the driving force for compaction is the differencebetween the fictive temperature and the process temperature experiencedby the glass during compaction. Thus, it would be desirable to minimizethe level of compaction in a glass substrate that is produced by afusion process as well as other forming processes (e.g., float).

There are two approaches to minimize compaction in glass. The first isto thermally pretreat the glass to create a fictive temperature similarto the one the glass will experience during the p-Si TFT manufacture.There are several difficulties with this approach. First, the multipleheating steps employed during the p-Si TFT manufacture create slightlydifferent fictive temperatures in the glass that cannot be fullycompensated for by this pretreatment. Second, the thermal stability ofthe glass becomes closely linked to the details of the p-Si TFTmanufacture, which could mean different pretreatments for differentend-users. Finally, pretreatment adds to processing costs andcomplexity.

Another approach is to slow the rate of strain at the processtemperature by increasing the viscosity of the glass. This can beaccomplished by raising the viscosity of the glass. The annealing pointrepresents the temperature corresponding to a fixed viscosity for aglass, and thus an increase in annealing point equates to an increase inviscosity at fixed temperature. The challenge with this approach,however, is the production of high annealing point glass that is costeffective. The main factors impacting cost are defects and assetlifetime. In a modern melter coupled to a fusion draw machine, fourtypes of defects are commonly encountered: (1) gaseous inclusions(bubbles or blisters); (2) solid inclusions from refractories or fromfailure to properly melt the batch; (3) metallic defects consistinglargely of platinum; and (4) devitrification products resulting from lowliquidus viscosity or excessive devitrification at either end of theisopipe. Glass composition has a disproportionate impact on the rate ofmelting, and hence on the tendency of a glass to form gaseous or soliddefects, and the oxidation state of the glass impacts the tendency toincorporate platinum defects. Devitrification of the glass on theforming mandrel or isopipe, can best be managed by selectingcompositions with high liquidus viscosities.

Asset lifetime is determined mostly by the rate of wear or deformationof the various refractory and precious metal components of the meltingand forming systems. Recent advances in refractory materials, platinumsystem design, and isopipe refractories have offered the potential togreatly extend the useful operational lifetime of a melter coupled to afusion draw machine. As a result, the lifetime-limiting component of amodern fusion draw melting and forming platform is the electrodes usedto heat the glass. Tin oxide electrodes corrode slowly over time, andthe rate of corrosion is a strong function both of temperature and glasscomposition. To maximize asset lifetime, it is desirable to identifycompositions that reduce the rate of electrode corrosion whilemaintaining the defect-limiting attributes described above.

As long as the compaction of a glass is below a threshold level, asignificant attribute determining the suitability of a glass as asubstrate is the variability, or lack thereof, in total pitch of thesubstrate during the manufacture of the TFT which can cause misalignmentof the components of the TFT and result in bad pixels in the finaldisplay. This variability is most significantly due to variations in thecompaction of the glass, variations in the elastic distortions of theglass under stress applied by the films deposited during the TFTmanufacture, and variations in the relaxation of those same stressesduring the TFT manufacturing. A glass possessing high dimensionalstability will have reduced variability of compaction as well as reducedstress relaxation, and a glass with a high Young's modulus will helpreduce the distortions due to film stress. Consequently, a glasspossessing both a high modulus and high dimensional stability willminimize total pitch variability during the TFT process, making it anadvantaged substrate for these applications.

While total pitch variability is a key attribute for the suitability ofa glass composition for use as a TFT backplane, other attributes arealso quite significant. After completion of the manufacturing of theTFTs, panel makers thin the display via an acid etch to reduce thethickness and weight of the final display. Consequently, a glass thatetches quickly in commercially available acid compositions would allowfor more economical thinning of the glass. Similarly, a glass with lowdensity would also help contribute to the desired reduction of weight ofthe final display.

Accordingly, there is a need in the art for glass compositions with ahigh Modulus and high dimensional stability while allowing reliablereduction in thickness and other advantageous properties andcharacteristics.

SUMMARY OF THE CLAIMS

One or more embodiments of the present disclosure are directed to glasscomprising, in mole percent on an oxide basis in the ranges: SiO₂68.5-72.0, Al₂O₃ greater than or equal to about 13.0, B₂O₃ less than orequal to about 2.5, MgO 1.0-6.0, CaO 4.0-8.0, SrO less than or equal toabout 4.5, BaO less than or equal to about 4.5, such that(MgO+CaO+SrO+BaO)/Al₂O₃ is less than or equal to about 1.6. The glasshas an etch index greater than or equal to about 23, an annealing pointgreater than or equal to about 800° C. and a Modulus greater than 82GPa.

One or more embodiments are directed to glass comprising, in molepercent on an oxide basis in the ranges: SiO₂ 63.0-71.0, Al₂O₃13.0-14.0, B₂O₃>0-3.0, MgO 0.9-9.0, CaO 5.25-6.5, SrO>0-6.0, BaO1.0-9.0, the glass substantially free of alkalis and having an etchindex >21 μm/mm³. In some embodiments, the glass comprises, in molepercent on an oxide basis, SiO₂ 68.0-71.0, B₂O₃>0-2.0, MgO 3.5-5.0,SrO>0-2.0, BaO 2.5-4.5.

One or more embodiments are directed to glass comprising, in molepercent on an oxide basis in the ranges: SiO₂ 68.0-70.5, Al₂O₃13.0-14.0, B₂O₃>0-3.0, MgO 0.9-9.0, CaO 5.25-11, SrO>0-6.0, BaO 1.0-9.0,wherein the glass substantially free of alkalis and having an etchindex >21 μm/mm³. In some embodiments, the glass comprises, in molepercent on an oxide basis, B₂O₃>0-2.0, MgO 3.5-5.0, CaO 5.25-10.0,SrO>0-2.0, BaO 2.5-4.5.

One or more embodiments are directed to glass comprising, in molepercent on an oxide basis in the ranges: SiO₂ 63.0-75.0, Al₂O₃13.0-14.0, B₂O₃>0-2.8, MgO 0.9-9.0, CaO 5.25-11, SrO>0-6.0, BaO 1.0-9.0,wherein the glass substantially free of alkalis and having an etchindex >21 μm/mm³. In some embodiments, the glass comprises, in molepercent on an oxide basis, SiO₂ 68.0-72.0, B₂O₃>0-2.0, MgO 3.5-5.0, CaO5.25-10.0, SrO>0-2.0, BaO 2.5-4.5.

One or more embodiments of the disclosure are directed to glasscomprising, in mole percent on an oxide basis in the ranges: SiO₂63.0-75.0, Al₂O₃ 13.0-14.0, B₂O₃>0-3.0, MgO 0.9-9.0, CaO 5.25-11,SrO>0-6.0, BaO 3.0-5.4, where the glass substantially free of alkalisand having an etch index >21 μm/mm³. In some embodiments, the glasscomprises, in mole percent on an oxide basis, SiO₂ 68.0-72.0,B₂O₃>0-2.0, MgO 3.5-5.0, CaO 5.25-10.0, SrO>0-2.0, BaO 2.5-4.5.

One or more embodiments of the disclosure are directed to glasscomprising, in mole percent on an oxide basis in the ranges: SiO₂63.0-75.0, Al₂O₃ 13.0-14.5, B₂O₃>0-2.0, MgO 0.9-9.0, CaO 5.0-6.5,SrO>0-6.0, BaO 1.0-9.0, the glass substantially free of alkalis, having(MgO+CaO+SrO+BaO)/Al₂O₃ 1.1-1.6 and an etch index >21 μm/mm³. In someembodiments, the glass comprises, in mole percent on an oxide basis,SiO₂ 68.0-72.0, MgO 3.5-5.0, CaO 5.25-6.5, SrO>0-2.0, BaO 2.5-4.5.

One or more embodiments are directed to glass comprising, in molepercent on an oxide basis in the ranges: SiO₂ 63.0-71.0, Al₂O₃13.0-14.0, B₂O₃>0-2.0, MgO 0.9-9.0, CaO 5.25-6.5, SrO>0-6.0, BaO1.0-9.0, where the glass substantially free of alkalis and having anetch index >21 μm/mm³. In some embodiments, the glass comprises, in molepercent on an oxide basis, SiO₂ 68.0-71.0, MgO 3.5-5.0, SrO>0-2.0, BaO2.5-4.5.

One or more embodiments are directed to glass comprising, in molepercent on an oxide basis in the ranges: SiO₂ 63.0-71.0, Al₂O₃13.0-14.0, B₂O₃>0-2.0, MgO 0.9-9.0, CaO 5.0-6.5, SrO>0-6.0, BaO 3.5-4.0,where the glass substantially free of alkalis and having an etchindex >21 μm/mm³. In some embodiments, the glass comprises, in molepercent on an oxide basis, SiO₂ 68.0-71.0, MgO 3.5-5.0, SrO>0-2.0.

One or more embodiments are directed to glass comprising, in molepercent on an oxide basis in the ranges: SiO₂ 63.0-71.0, Al₂O₃13.0-14.0, B₂O₃>0-2.0, MgO 0.9-9.0, CaO 5.0-6.5, SrO>0-6.0, BaO 1.0-9.0,the sum of CaO and BaO>8.6, where the glass substantially free ofalkalis and having an etch index >21 μm/mm³. In some embodiments, theglass comprises, in mole percent on an oxide basis, SiO₂ 68.0-71.0, MgO3.5-5.0, SrO>0-2.0, BaO 2.5-4.5.

Additional embodiments of the present disclosure are directed to glasshaving an annealing temperature greater than or equal to about 785° C.;a density less than or equal to about 2.65 g/cc; a T_(200P) less than orequal to about 1750° C.; a T_(35kP) less than or equal to about 1340°C.; a Young's modulus greater than or equal to about 82 GPa; and an etchindex greater than or equal to about 21 μm/mm³ as defined by theequation:−54.6147+(2.50004)*(Al₂O₃)+(1.3134)*(B₂O₃)+(1.84106)*(MgO)+(3.01223)*(CaO)+(3.7248)*(SrO)+(4.13149)*(BaO),wherein the glass is substantially free of alkalis. In some embodiments,the glass has one or more of an annealing temperature greater than orequal to about 800° C.; a density less than or equal to about 2.61 g/cc;a T_(200P) less than or equal to about 1700° C.; a T_(35kP) less than orequal to about 1310° C.; and/or an etch index is greater than or equalto about 21 μm/mm³. In various embodiments, the glass comprises one ormore of: SiO₂, in mole percent on an oxide basis, in the range68.1-72.3; Al₂O₃, in mole percent on an oxide basis, in the range11.0-14.0; B₂O₃, in mole percent on an oxide basis, in the range >0-3.0;MgO, in mole percent on an oxide basis, in the range 1.0-7.2; MgO, inmole percent on an oxide basis, in the range 3.1-5.8; CaO, in molepercent on an oxide basis, in the range 4.1-10.0; CaO, in mole percenton an oxide basis, in the range 4.5-7.4; SrO, in mole percent on anoxide basis, in the range >0-4.2; SrO, in mole percent on an oxidebasis, in the range >0-2.0; BaO, in mole percent on an oxide basis, inthe range 1.2-4.4; and/or BaO, in mole percent on an oxide basis, in therange 2.6-4.4. In some embodiments, the glass comprises, in mole percenton an oxide basis, SiO₂ 68.0-72.0, B₂O₃ 0.1-3.0 and CaO 5.0-6.5. In oneor more embodiments, the glass comprises, in mole percent on an oxidebasis, Al₂O₃ 13.0-14.0, B₂O₃ 0.1-3.0 and CaO 5.25-6.0.

Some embodiments of the disclosure are directed to glass that issubstantially free of alkalis. The glass comprises, in mol % on an oxidebasis, SiO₂ 69.76-71.62, Al₂O₃ 11.03-13.57, B₂O₃ 0-2.99, MgO 3.15-5.84,CaO 4.55-7.35, SrO 0.2-1.99, BaO 2.61-4.41 and ZnO 0-1.0, wherein theratio of (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6and the ratio of MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and0.37.

One or more embodiments of the disclosure are directed to glasssubstantially free of alkalis comprising in mol % on an oxide basis:SiO₂ 68.14-72.29, Al₂O₃ 11.03-14.18, B₂O₃ 0-2.99, MgO 1.09-7.2, CaO4.12-9.97, SrO 0.2-4.15, BaO 1.26-4.41 and ZnO 0-1.0, wherein the ratioof (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6 and theratio of MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and 0.37.

Some embodiments of the disclosure are directed to glass that issubstantially free of alkalis. The glass has a ratio of(MgO+CaO+SrO+BaO)/Al₂O₃ in the range of about 1.0 and 1.6, the ratio ofMgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and 0.37,T(ann)>785° C., density <2.65 g/cc, T(200P)<1750° C., T(35 kP)<1340° C.,Young's modulus >82 GPa, and etch index >21 μm/mm³.

Additional embodiments of the disclosure are directed to glass that issubstantially free of alkalis wherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in therange of about 1.0 and 1.6, the ratio of MgO/(MgO+CaO+SrO+BaO) is in therange of about 0.22 and 0.37 and the etch index >21 μm/mm³.

In one or more embodiments, glass that is substantially free of alkalishas a (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6, theratio of MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and 0.37and a liquidus viscosity >150 kP.

Some embodiments of the disclosure are directed to glass that issubstantially free of alkalis wherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in therange of about 1.0 and about 1.6, an etch index greater than or equal to21 μm/mm³, T(ann)>800° C. and Young's modulus >82 GPa.

Further embodiments of the disclosure are directed to aluminosilicateglass articles that are substantially free of alkalis. The glassarticles have: an annealing temperature greater than or equal to about795° C.; a density less than or equal to about 2.63 g/cc; a T_(200P)less than or equal to about 1730° C.; a T_(35kP) less than or equal toabout 1320° C.; a Young's modulus greater than or equal to about 81.5GPa; and an etch index greater than or equal to about 23 μm/mm³.

Additional embodiments of the disclosure are directed to aluminosilicateglass articles that are substantially free of alkalis. The articleshave: an annealing temperature greater than or equal to about 800° C.; adensity less than or equal to about 2.61 g/cc; a T_(200P) less than orequal to about 1710° C.; a T_(35kP) less than or equal to about 1310°C.; a Young's modulus greater than or equal to about 81.2 GPa; and anetch index greater than or equal to about 23 μm/mm³.

Additional embodiments of the disclosure are directed to an objectcomprising the glass produced by a downdraw sheet fabrication process.Further embodiments are directed to glass produced by the fusion processor variants thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying figures, which are incorporated in and constitute apart of this specification, illustrate several embodiments describedbelow.

FIG. 1 shows a schematic representation of a forming mandrel used tomake precision sheet in the fusion draw process;

FIG. 2 shows a cross-sectional view of the forming mandrel of FIG. 1taken along position 6; and

FIG. 3 shows spectra for 1200° and 1140° C. blackbodies and thetransmission spectrum of 0.7 mm thick Eagle XG® amorphous thin-filmtransistor substrate.

DETAILED DESCRIPTION

Described herein are alkali-free glasses and methods for making the samethat possess high annealing points and high Young's moduli, allowing theglasses to possess excellent dimensional stability (i.e., lowcompaction) during the manufacture of TFTs, reducing variability duringthe TFT process. Glass with high annealing points can help prevent paneldistortion due to compaction/shrinkage during thermal processingsubsequent to manufacturing of the glass. Additionally, some embodimentsof the present disclosure have high etch rates, allowing for theeconomical thinning of the backplane, as well as unusually high liquidusviscosities, thus reducing or eliminating the likelihood ofdevitrification on the relatively cold forming mandrel. As a result ofspecific details of their composition, exemplary glasses melt to goodquality with very low levels of gaseous inclusions, and with minimalerosion to precious metals, refractories, and tin oxide electrodematerials.

In one embodiment, the substantially alkali-free glasses can have highannealing points. In some embodiments, the annealing point is greaterthan about 785° C., 790° C., 795° C. or 800° C. Without being bound byany particular theory of operation, it is believed that such highannealing points result in low rates of relaxation—and hencecomparatively small amounts of compaction—for exemplary glasses to beused as backplane substrate in a low-temperature polysilicon process.

In another embodiment, the temperature of exemplary glasses at aviscosity of about 35,000 poise (T_(35k)) is less than or equal to about1340° C., 1335° C., 1330° C., 1325° C., 1320° C., 1315° C., 1310° C.,1300° C. or 1290° C. In specific embodiments, the glass has a viscosityof about 35,000 poise (T_(35k)) less than about 1310° C. In otherembodiments, the temperature of exemplary glasses at a viscosity ofabout 35,000 poise (T_(35k)) is less than about 1340° C., 1335° C.,1330° C., 1325° C., 1320° C., 1315° C., 1310° C., 1300° C. or 1290° C.In various embodiments, the glass article has a T_(35k) in the range ofabout 1275° C. to about 1340° C., or in the range of about 1280° C. toabout 1315° C.

The liquidus temperature of a glass (T_(liq)) is the temperature abovewhich no crystalline phases can coexist in equilibrium with the glass.In various embodiments, a glass articles has a T_(liq) in the range ofabout 1180° C. to about 1290° C., or in the range of about 1190° C. toabout 1280° C. In another embodiment, the viscosity corresponding to theliquidus temperature of the glass is greater than or equal to about150,000 poise. In some embodiments, the viscosity corresponding to theliquidus temperature of the glass is greater than or equal to about175,000 poise, 200,000 poise, 225,000 poise or 250,000 poise.

In another embodiment, an exemplary glass can provideT_(35k)−T_(liq)>0.25 T_(35k)−225° C. This ensures minimum tendency todevitrify on the forming mandrel of the fusion process.

In one or more embodiments, the substantially alkali-free glasscomprises in mole percent on an oxide basis:

-   -   SiO₂ 60-80    -   Al₂O₃ 5-20    -   B₂O₃ 0-10    -   MgO 0-20    -   CaO 0-20    -   SrO 0-20    -   BaO 0-20    -   ZnO 0-20        where Al₂O₃, MgO, CaO, SrO, BaO represent the mole percents of        the respective oxide components.

In some embodiments, the substantially alkali-free glass comprises inmole percent on an oxide basis:

-   -   SiO₂ 65-75    -   Al₂O₃ 10-15    -   B₂O₃ 0-3.5    -   MgO 0-7.5    -   CaO 4-10    -   SrO 0-5    -   BaO 1-5    -   ZnO 0-5        wherein        1.0≤(MgO+CaO+SrO+BaO)/Al₂O₃<2 and 0<MgO/(MgO+Ca+SrO+BaO)<0.5.

In certain embodiments, the substantially alkali-free glass comprises inmole percent on an oxide basis:

-   -   SiO₂ 67-72    -   Al₂O₃ 11-14    -   B₂O₃ 0-3    -   MgO 3-6    -   CaO 4-8    -   SrO 0-2    -   BaO 2-5    -   ZnO 0-1        wherein        1.0≤(MgO+CaO+SrO+BaO)/Al₂O₃<1.6 and        0.20<MgO/(MgO+Ca+SrO+BaO)<0.40.

In one embodiment, the glass includes a chemical fining agent. Suchfining agents include, but are not limited to, SnO₂, As₂O₃, Sb₂O₃, F, Cland Br, and in which the concentrations of the chemical fining agentsare kept at a level of 0.5 mol % or less. In some embodiments, thechemical fining agent comprises one or more of SnO₂, As₂O₃, Sb₂O₃, F, Clor Br in a concentration less than or equal to about 0.5 mol %, 0.45 mol%, 0.4 mol %, 0.35 mol %, 0.3 mol % or 0.25 mol %. Chemical finingagents may also include CeO₂, Fe₂O₃, and other oxides of transitionmetals, such as MnO₂. These oxides may introduce color to the glass viavisible absorptions in their final valence state(s) in the glass, andthus their concentration may be at a level of 0.2 mol % or less. In oneor more embodiments, the glass composition comprises one or more oxidesof transition metals in a concentration less than or equal to about 0.2mol %, 0.15 mol %, 0.1 mol % or 0.05 mol %. In some embodiments, theglass composition comprises in the range of about 0.01 mol % to about0.4 mol % of any one or combination of SnO₂, As₂O₃, Sb₂O₃, F, Cl and/orBr. In specific embodiments, the glass composition comprises in therange of about 0.005 mol % to about 0.2 mol % of any one or combinationof Fe₂O₃, CeO₂ and/or MnO₂. In some embodiments, As₂O₃ and Sb₂O₃comprises less than or equal to about 0.005 mol % of the glasscomposition.

In one embodiment, exemplary glasses are manufactured into sheet via thefusion process. The fusion draw process may result in a pristine,fire-polished glass surface that reduces surface-mediated distortion tohigh resolution TFT backplanes and color filters. FIG. 1 is a schematicdrawing of a forming mandrel, or isopipe, in a non-limiting fusion drawprocess. FIG. 2 is a schematic cross-section of the isopipe nearposition 6 in FIG. 1. Glass is introduced from the inlet 1, flows alongthe bottom of the trough 4 formed by the weir walls 9 to the compressionend 2. Glass overflows the weir walls 9 on either side of the isopipe(see FIG. 2), and the two streams of glass join or fuse at the root 10.Edge directors 3 at either end of the isopipe serve to cool the glassand create a thicker strip at the edge called a bead. The bead is pulleddown by pulling rolls, hence enabling sheet formation at high viscosity.By adjusting the rate at which sheet is pulled off the isopipe, it ispossible to use the fusion draw process to produce a very wide range ofthicknesses at a fixed melting rate.

The downdraw sheet drawing processes and, in particular, the fusionprocess described in U.S. Pat. Nos. 3,338,696 and 3,682,609 (both toDockerty), which are incorporated by reference, can be used herein.Without being bound by any particular theory of operation, it isbelieved that the fusion process can produce glass substrates that donot require polishing. Current glass substrate polishing is capable ofproducing glass substrates having an average surface roughness greaterthan about 0.5 nm (Ra), as measured by atomic force microscopy. Theglass substrates produced by the fusion process have an average surfaceroughness as measured by atomic force microscopy of less than 0.5 nm.The substrates also have an average internal stress as measured byoptical retardation which is less than or equal to 150 psi. Of course,the claims appended herewith should not be so limited to fusionprocesses as embodiments described herein are equally applicable toother forming processes such as, but not limited to, float formingprocesses.

In one embodiment, exemplary glasses are manufactured into sheet formusing the fusion process. While exemplary glasses are compatible withthe fusion process, they may also be manufactured into sheets or otherware through different manufacturing processes. Such processes includeslot draw, float, rolling, and other sheet-forming processes known tothose skilled in the art.

Relative to these alternative methods for creating sheets of glass, thefusion process as discussed above is capable of creating very thin, veryflat, very uniform sheets with a pristine surface. Slot draw also canresult in a pristine surface, but due to change in orifice shape overtime, accumulation of volatile debris at the orifice-glass interface,and the challenge of creating an orifice to deliver truly flat glass,the dimensional uniformity and surface quality of slot-drawn glass aregenerally inferior to fusion-drawn glass. The float process is capableof delivering very large, uniform sheets, but the surface issubstantially compromised by contact with the float bath on one side,and by exposure to condensation products from the float bath on theother side. This means that float glass must be polished for use in highperformance display applications.

The fusion process may involve rapid cooling of the glass from hightemperature, resulting in a high fictive temperature T_(f): The fictivetemperature can be thought of as representing the discrepancy betweenthe structural state of the glass and the state it would assume if fullyrelaxed at the temperature of interest. Reheating a glass with a glasstransition temperature T_(g) to a process temperature T_(p) such thatT_(p)<T_(g)≤T_(f) may be affected by the viscosity of the glass. SinceT_(p)<T_(f), the structural state of the glass is out of equilibrium atT_(p), and the glass will spontaneously relax toward a structural statethat is in equilibrium at T_(p). The rate of this relaxation scalesinversely with the effective viscosity of the glass at T_(p), such thathigh viscosity results in a slow rate of relaxation, and a low viscosityresults in a fast rate of relaxation. The effective viscosity variesinversely with the fictive temperature of the glass, such that a lowfictive temperature results in a high viscosity, and a high fictivetemperature results in a comparatively low viscosity. Therefore, therate of relaxation at T_(p) scales directly with the fictive temperatureof the glass. A process that introduces a high fictive temperatureresults in a comparatively high rate of relaxation when the glass isreheated at T_(p).

One means to reduce the rate of relaxation at T_(p) is to increase theviscosity of the glass at that temperature. The annealing point of aglass represents the temperature at which the glass has a viscosity of10^(13.2) poise. As temperature decreases below the annealing point, theviscosity of the supercooled melt increases. At a fixed temperaturebelow T_(g), a glass with a higher annealing point has a higherviscosity than a glass with a lower annealing point. Therefore,increasing the annealing point may increase the viscosity of a substrateglass at T_(p). Generally, the composition changes necessary to increasethe annealing point also increase viscosity at all other temperatures.In a non-limiting embodiment, the fictive temperature of a glass made bythe fusion process corresponds to a viscosity of about 10¹¹-10¹² poise,so an increase in annealing point for a fusion-compatible glassgenerally increases its fictive temperature as well. For a given glassregardless of the forming process, higher fictive temperature results inlower viscosity at temperature below T_(g), and thus increasing fictivetemperature works against the viscosity increase that would otherwise beobtained by increasing the annealing point. To have a substantial changein the rate of relaxation at T_(p), it is generally necessary to makerelatively large changes in the annealing point. An aspect of exemplaryglasses is that it has an annealing point greater than or equal to about785° C., or 790° C., or 795° C. or 800° C., or 805° C., or 810° C., or815° C., or in the range of about 796.1° C. to about 818.3° C. Withoutbeing bound by any particular theory of operation, it is believed thatsuch high annealing points results in acceptably low rates of thermalrelaxation during low-temperature TFT processing, e.g., typicallow-temperature polysilicon rapid thermal anneal cycles.

In addition to its impact on fictive temperature, increasing annealingpoint also increases temperatures throughout the melting and formingsystem, particularly the temperatures on the isopipe. For example, EagleXG® glass and Lotus™ glass (Corning Incorporated, Corning, N.Y.) haveannealing points that differ by about 50° C., and the temperature atwhich they are delivered to the isopipe also differ by about 50° C. Whenheld for extended periods of time above about 1310° C., zirconrefractory forming the isopipe shows thermal creep, which can beaccelerated by the weight of the isopipe itself plus the weight of theglass on the isopipe. A second aspect of exemplary glasses is that theirdelivery temperatures are less than or equal to about 1350° C., or 1345°C., or 1340° C., or 1335° C., or 1330° C., or 1325° C., or 1320° C., or1315° C. or 1310° C. Such delivery temperatures may permit extendedmanufacturing campaigns without a need to replace the isopipe or extendthe time between isopipe replacements.

In manufacturing trials of glasses with high annealing points anddelivery temperatures below 1350° C. and below 1310° C., it has beenfound that the glass showed a greater tendency toward devitrification onthe root of the isopipe and—especially—the edge directors relative toglasses with lower annealing points. Careful measurement of thetemperature profile on the isopipe showed that the edge directortemperatures were much lower relative to the center root temperaturethan had been anticipated and is believed to be due to radiative heatloss. The edge directors typically are maintained at a temperature belowthe center root temperature to ensure that the glass is viscous enoughas it leaves the root to put the sheet in between the edge directorsunder tension, thus maintaining a flat shape. As edge directors arelocated at either end of the isopipe, the edge directors are difficultto heat, and thus the temperature difference between the center of theroot and the edge directors may differ by 50° or more.

While not wishing to be held to theory, it is believed that theincreased tendency toward devitirication in the fusion process can beunderstood in terms of the radiative heat loss of glass as a function oftemperature. Fusion is substantially an isothermal process, so glassexits the inlet at a particular viscosity and exits the root at a muchhigher viscosity, but the actual values for the viscosity are notstrongly dependent on the identity of the glass or the temperature ofthe process. Thus, a glass with a higher annealing point generallyrequires much higher isopipe temperatures than a glass with a lowerannealing point just to match the delivery and exit viscosities. As anexample, FIG. 3 shows blackbody spectra corresponding to 1140° C. and1200° C., approximately the temperature at the root of the isopipe (10in FIG. 2) for Eagle XG® glass and Lotus™ glass, respectively. Thevertical line at about 2.5 μm corresponds approximately with the startof the infrared cut-off, the region in the near infrared through whichoptical absorption in a borosilicate glass rises very steeply to a high,nearly constant value. At wavelengths shorter than the cut-offwavelength, a glass is sensibly transparent to a wavelength between 300and 400 nm, the UV cut-off. Between about 300 nm and about 2.5 μm, the1200° C. blackbody has a greater absolute energy, and a larger fractionof its total energy than the 1140° C. blackbody. Since the glass issensibly transparent through this wavelength range, the radiative heatloss from a glass at 1200° C. is much greater than that of a glass at1140° C.

Again, without being bound by any particular theory of operation, it isbelieved that since radiative heat loss increases with temperature, andsince high annealing point glasses generally are formed at highertemperatures than lower annealing point glasses, the temperaturedifference between the center root and the edge director generallyincreases with the annealing point of the glass. This may have a directrelationship to the tendency of a glass to form devitrification productson the isopipe or edge directors.

The liquidus temperature of a glass is defined as the highesttemperature at which a crystalline phase would appear if a glass wereheld indefinitely at that temperature. The liquidus viscosity is theviscosity of a glass at the liquidus temperature. To completely avoiddevitrification on an isopipe, it may be helpful for the liquidusviscosity to be high enough to ensure that glass is no longer on theisopipe refractory or edge director material at or near the liquidustemperature.

In practice, few alkali-free glasses have liquidus viscosities of thedesired magnitude. Experience with substrate glasses suitable foramorphous silicon applications (e.g., Eagle XG® glass) indicated thatedge directors could be held continuously at temperatures up to 60°below the liquidus temperature of certain alkali-free glasses. While itwas understood that glasses with higher annealing points would requirehigher forming temperatures, it was not anticipated that the edgedirectors would be so much cooler relative to the center roottemperature. A useful metric for keeping track of this effect is thedifference between the delivery temperature onto the isopipe and theliquidus temperature of the glass, T_(liq). In the fusion process, it isgenerally desirable to deliver glass at about 35,000 poise (T_(35k)).For a particular delivery temperature, it may be useful to makeT_(35k)−T_(liq) as large possible, but for an amorphous siliconsubstrate such as Eagle XG® glass, it is found that extendedmanufacturing campaigns can be conducted if T_(35k)−T_(liq) is about 80°or more. As temperature increases, T_(35k)−T_(liq) must increase aswell, such that for T_(35k) near 1300° C., it may be helpful to haveT_(35k)−T_(liq) equal to or greater than about 100° C. The minimumuseful value for T_(35k)−T_(liq) varies approximately linearly withtemperature from about 1200° C. to about 1320° C., and can be expressedaccording to equation (1).Minimum T _(35k) −T _(liq)=0.25T _(35k)−225,  (1)where all temperatures are in ° C. Thus, one or more embodiments ofexemplary glasses has a T_(35k)−T_(liq)>0.25 T_(35k)−225° C.

In addition, the forming process may require glass with a high liquidusviscosity. This is necessary so as to avoid devitrification products atinterfaces with glass and to minimize visible devitrification productsin the final glass. Thus, for a given glass compatible with fusion for aparticular sheet size and thickness, adjusting the process so as tomanufacture wider sheet or thicker sheet generally results in lowertemperatures at either end of the isopipe. Some embodiments have higherliquidus viscosities to provide greater flexibility for manufacturingvia the fusion process. In some embodiments, the liquidus viscosity isgreater than or equal to about 150 kP.

In tests of the relationship between liquidus viscosity and subsequentdevitrification tendencies in the fusion process, the inventors havesurprisingly found that high delivery temperatures, such as those ofexemplary glasses, generally require higher liquidus viscosities forlong-term production than would be the case for typical AMLCD substratecompositions with lower annealing points. While not wishing to be boundby theory, it is believed that this arises from accelerated rates ofcrystal growth as temperature increases. Fusion is essentially anisoviscous process, so a more viscous glass at some fixed temperaturemay be formed by fusion at higher temperature than a less viscous glass.While some degree of undercooling (cooling below the liquidustemperature) can be sustained for extended periods in a glass at lowertemperature, crystal growth rates increase with temperature, and thusmore viscous glasses grow an equivalent, unacceptable amount ofdevitrification products in a shorter period of time than less viscousglasses. Depending on where formed, devitrification products cancompromise forming stability and introduce visible defects into thefinal glass.

To be formed by the fusion process, one or more embodiments of the glasscompositions have a liquidus viscosity greater than or equal to about150,000 poises, or 175,000 poises, or 200,000 poises. A surprisingresult is that throughout the range of exemplary glasses, it is possibleto obtain a liquidus temperature low enough, and a viscosity highenough, such that the liquidus viscosity of the glass is unusually highcompared to other compositions.

In the glass compositions described herein, SiO₂ serves as the basicglass former. In certain embodiments, the concentration of SiO₂ can begreater than 60 mole percent to provide the glass with a density andchemical durability suitable for a flat panel display glass (e.g., anAMLCD glass), and a liquidus temperature (liquidus viscosity), whichallows the glass to be formed by a downdraw process (e.g., a fusionprocess). In terms of an upper limit, in general, the SiO₂ concentrationcan be less than or equal to about 80 mole percent to allow batchmaterials to be melted using conventional, high volume, meltingtechniques, e.g., Joule melting in a refractory melter. As theconcentration of SiO₂ increases, the 200 poise temperature (meltingtemperature) generally rises. In various applications, the SiO₂concentration is adjusted so that the glass composition has a meltingtemperature less than or equal to 1,750° C. In some embodiments, theSiO₂ concentration is in the range of about 63.0 mol % to about 75.0 mol%, or in the range of about 63.0 mol % to about 71.0 mol %, or in therange of about 65.0 mol % to about 73 mol % or in the range of about 67mol % and 72 mol %, or in the range of about 68.0 to 72.0 mol %, or inthe range of about 68.0 mol % to about 71.0 mol %, or in the range ofabout 68.0 mol % to about 70.5 mol %, or in the range of about 68.1 mol% to about 72.3 mol %, or in the range of about 68.5 to about 72.0 mol%, or in the range of about 68.95 mol % to about 71.12 mol %, or in therange of about 69.7 to about 71.7 mol %.

Al₂O₃ is another glass former used to make the glasses described herein.An Al₂O₃ concentration greater than or equal to 10 mole percent providesthe glass with a low liquidus temperature and high viscosity, resultingin a high liquidus viscosity. The use of at least 10 mole percent Al₂O₃also improves the glass's annealing point and modulus. In order that theratio (MgO+CaO+SrO+BaO)/Al₂O₃ is greater than or equal to 1.0, the Al₂O₃concentration may be below about 15 mole percent. In some embodiments,the Al₂O₃ concentration is in the range of about 11.0 and 14.0 molepercent, or in the range of about 11.0 to about 13.6 mol %, or in therange of about 13.0 mol % to about 14.5 mol %, or in the range of about13.0 mol % to about 14.0 mol %, or in the range of about 13.0 mol % toabout 14.18 mol %. In some embodiments, the Al₂O₃ concentration isgreater than or equal to about 9.5 mol %, 10.0 mol %, 10.5 mol %, 11.0mol %, 11.5 mol %, 12.0 mol %, 12.5 mol % or 13.0 mol % whilemaintaining a ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ greater than or equal toabout 1.0.

Some embodiments of the disclosure have a modulus greater than about 81GPa, or 81.5 GPa, or 82 GPa, or 82.5 GPa, or 83 GPa, or 83.5 GPa, or 84GPa, or 84.5 GPa or 85 GPa. In various embodiments, an aluminosilicateglass article has a Young's modulus in the range of about 81 GPa toabout 88 GPa, or in the range of about 81.5 GPa to about 85 GPa, or inthe range of about 82 GPa to about 84.5 GPa.

The density of some embodiments of aluminosilicate glass articles isless than about 2.7 g/cc, or 2.65 g/cc, or 2.61 g/cc, or 2.6 g/cc, or2.55 g/cc. In various embodiments, the density is in the range of about2.55 g/cc to about 2.65 g/cc, or in the range of about 2.57 g/cc toabout 2.626 g/cc.

B₂O₃ is both a glass former and a flux that aids melting and lowers themelting temperature. It has an impact on both liquidus temperature andviscosity. Increasing B₂O₃ can be used to increase the liquidusviscosity of a glass. To achieve these effects, the glass compositionsof one or more embodiments may have B₂O₃ concentrations that are equalto or greater than 0.1 mole percent. As discussed above with regard toSiO₂, glass durability is very important for LCD applications.Durability can be controlled somewhat by elevated concentrations ofalkaline earth oxides, and significantly reduced by elevated B₂O₃content Annealing point decreases as B₂O₃ increases, so it may behelpful to keep B₂O₃ content low relative to its typical concentrationin amorphous silicon substrates. Thus in some embodiments, the glasscomposition has B₂O₃ concentrations that are in the range of about 0.0and 3.0 mole percent, or greater than 0 to about 3.0 mol %, or about 0.0to about 2.8 mol %, or greater than 0 to about 2.8 mol %, or about 0.0to about 2.5 mol %, or greater than 0 to about 2.5 mol %, or in therange of about 0.0 to about 2.0 mol %, or greater than 0 to about 2.0mol percent, or in the range of about 0.1 mol % to about 3.0 mol %, orin the range of about 0.75 mol % to about 2.13 mol %.

The Al₂O₃ and B₂O₃ concentrations can be selected as a pair to increaseannealing point, increase modulus, improve durability, reduce density,and reduce the coefficient of thermal expansion (CTE), while maintainingthe melting and forming properties of the glass.

For example, an increase in B₂O₃ and a corresponding decrease in Al₂O₃can be helpful in obtaining a lower density and CTE, while an increasein Al₂O₃ and a corresponding decrease in B₂O₃ can be helpful inincreasing annealing point, modulus, and durability, provided that theincrease in Al₂O₃ does not reduce the (MgO+CaO+SrO+BaO)/Al₂O₃ ratiobelow about 1.0. For (MgO+CaO+SrO+BaO)/Al₂O₃ ratios below about 1.0, itmay be difficult or impossible to remove gaseous inclusions from theglass due to late-stage melting of the silica raw material. Furthermore,when (MgO+CaO+SrO+BaO)/Al₂O₃≤1.05, mullite, an aluminosilicate crystal,can appear as a liquidus phase. Once mullite is present as a liquidusphase, the composition sensitivity of liquidus increases considerably,and mullite devitrification products both grow very quickly and are verydifficult to remove once established. Thus, in some embodiments, theglass composition has (MgO+CaO+SrO+BaO)/Al₂O₃≥1.0 (or greater than orequal to about 1.0). In various embodiments, the glass has(MgO+CaO+SrO+BaO)/Al₂O₃≥1.05 (or greater than or equal to about 1.05),or in the range of about 1 to about 1.17.

In one or more embodiments, glasses for use in AMLCD applications havecoefficients of thermal expansion (CTEs) (22-300° C.) in the range ofabout 28×10⁻⁷/° C. to about 42×10⁻⁷/° C., or in the range of about30×10⁻⁷/° C. to about 40×10⁻⁷/° C., or in the range of about 32×10⁻⁷/°C. to about 38×10⁻⁷/° C.

In addition to the glass formers (SiO₂, Al₂O₃, and B₂O₃), the glassesdescribed herein also include alkaline earth oxides. In one embodiment,at least three alkaline earth oxides are part of the glass composition,e.g., MgO, CaO, and BaO, and, optionally, SrO. The alkaline earth oxidesprovide the glass with various properties important to melting, fining,forming, and ultimate use. Accordingly, to improve glass performance inthese regards, in one embodiment, the (MgO+CaO+SrO+BaO)/Al₂O₃ ratio isgreater than or equal to about 1.0. As this ratio increases, viscositytends to increase more strongly than liquidus temperature, and thus itis increasingly difficult to obtain suitably high values forT_(35k)−T_(liq). Thus in another embodiment, ratio(MgO+CaO+SrO+BaO)/Al₂O₃ is less than or equal to about 2. In someembodiments, the (MgO+CaO+SrO+BaO)/Al₂O₃ ratio is in the range of about1 to about 1.2, or in the range of about 1 to about 1.16, or in therange of about 1.1 to about 1.6. In detailed embodiments, the(MgO+CaO+SrO+BaO)/Al₂O₃ ratio less than about 1.7, or 1.6, or 1.5.

For certain embodiments of this disclosure, the alkaline earth oxidesmay be treated as what is in effect a single compositional component.This is because their impact upon viscoelastic properties, liquidustemperatures and liquidus phase relationships are qualitatively moresimilar to one another than they are to the glass forming oxides SiO₂,Al₂O₃ and B₂O₃. However, the alkaline earth oxides CaO, SrO and BaO canform feldspar minerals, notably anorthite (CaAl₂Si₂O₈) and celsian(BaAl₂Si₂O₈) and strontium-bearing solid solutions of same, but MgO doesnot participate in these crystals to a significant degree. Therefore,when a feldspar crystal is already the liquidus phase, a superadditionof MgO may serves to stabilize the liquid relative to the crystal andthus lower the liquidus temperature. At the same time, the viscositycurve typically becomes steeper, reducing melting temperatures whilehaving little or no impact on low-temperature viscosities.

The inventors have found that the addition of small amounts of MgO maybenefit melting by reducing melting temperatures, forming by reducingliquidus temperatures and increasing liquidus viscosity, whilepreserving high annealing point and, thus, low compaction. In variousembodiments, the glass composition comprises MgO in an amount in therange of about 0.9 mol % to about 9 mol %, or in the range of about 1.0mol % to about 7.2 mol %, or in the range of about 1.0 mol % to about6.0 mol %, or in the range of about 2.1 mol % to about 5.68 mol %, or inthe range of about 3.1 mol % to about 5.9 mol %, or in the range ofabout 3.5 mol % to about 5.0 mol %.

The inventors have surprisingly found that glasses with suitably highvalues of T_(35k)−T_(liq), the ratio of MgO to the other alkalineearths, MgO/(MgO+CaO+SrO+BaO), falls within a relatively narrow range.As noted above, additions of MgO can destabilize feldspar minerals, andthus stabilize the liquid and lower liquidus temperature. However, onceMgO reaches a certain level, mullite, Al₆Si₂O₁₃, may be stabilized, thusincreasing the liquidus temperature and reducing the liquidus viscosity.Moreover, higher concentrations of MgO tend to decrease the viscosity ofthe liquid, and thus even if the liquidus viscosity remains unchanged byaddition of MgO, it will eventually be the case that the liquidusviscosity will decrease. Thus in another embodiment,0.20≤MgO/(MgO+CaO+SrO+BaO)≤0.40 or in some embodiments,0.22≤MgO/(MgO+CaO+SrO+BaO)≤0.37. Within these ranges, MgO may be variedrelative to the glass formers and the other alkaline earth oxides tomaximize the value of T_(35k)−T_(liq) consistent with obtaining otherdesired properties.

Without being bound by any particular theory of operation, it isbelieved that calcium oxide present in the glass composition can producelow liquidus temperatures (high liquidus viscosities), high annealingpoints and moduli, and CTE's in the most desired ranges for flat panelapplications, specifically, AMLCD applications. It also contributesfavorably to chemical durability, and compared to other alkaline earthoxides, it is relatively inexpensive as a batch material. However, athigh concentrations, CaO increases the density and CTE. Furthermore, atsufficiently low SiO₂ concentrations, CaO may stabilize anorthite, thusdecreasing liquidus viscosity. Accordingly, in one or more embodiment,the CaO concentration can be greater than or equal to 4 mole percent, or4.0 mol %. In various embodiments, the CaO concentration of the glasscomposition is in the range of about 4.0 mol % to about 8.0 mol %, or inthe range of about 4.1 mol % to about 10 mol % (or 10.0 mol %), or inthe range of about 4.12 mol % to about 7.45 mol %, or in the range ofabout 4.5 mol % to about 7.4 mol %, or in the range of about 5.0 mol %to about 6.5 mol %, or in the range of about 5.25 mol % to about 11 mol% (or 11.0 mol %), or in the range of about 5.25 mol % to about 10 mol %(or 10.0 mol %), or in the range of about 5.25 mol % to about 6.5 mol %,or in the range of about 5.25 mol % to about 6.0 mol %.

SrO and BaO can both contribute to low liquidus temperatures (highliquidus viscosities) and, thus, the glasses described herein willtypically contain at least both of these oxides. However, the selectionand concentration of these oxides are selected to avoid an increase inCTE and density and a decrease in modulus and annealing point. Therelative proportions of SrO and BaO can be balanced so as to obtain asuitable combination of physical properties and liquidus viscosity suchthat the glass can be formed by a downdraw process. In variousembodiments, the glass comprises SrO in the range of about 0 to about6.0 mol %, or greater than 0 to about 6.0 mol %, or about 0 to about 4.5mol %, 4.2 mol %, or 2.0 mol %, or greater than 0 to about 4.5 mol %,4.2 mol % or 2.0 mol %, or in the range of about 0.45 mol % to about4.15 mol %. In some embodiments, the minimum amount of SrO is about 0.02mol %. In one or more embodiments, the glass comprises BaO in the rangeof about 0 to about 4.5 mol %, or greater than 0 to about 4.5 mol %, orabout 1.0 to about 9.0 mol %, or about 1.2 mol % to about 4.4 mol %, orabout 2.42 mol % to about 4.3 mol %, or about 2.5 mol % to about 4.5 mol%, or about 2.6 mol % to about 4.4 mol %, or about 3.0 mol % to about5.4 mol %, or about 3.5 mol % to about 4.0 mol %.

To summarize the effects/roles of the central components of the glassesof the disclosure, SiO₂ is the basic glass former. Al₂O₃ and B₂O₃ arealso glass formers and can be selected as a pair with, for example, anincrease in B₂O₃ and a corresponding decrease in Al₂O₃ being used toobtain a lower density and CTE, while an increase in Al₂O₃ and acorresponding decrease in B₂O₃ being used in increasing annealing point,modulus, and durability, provided that the increase in Al₂O₃ does notreduce the RO/Al₂O₃ ratio below about 1.0, where RO=(MgO+CaO+SrO+BaO).If the ratio goes too low, meltability is compromised, i.e., the meltingtemperature becomes too high. B₂O₃ can be used to bring the meltingtemperature down, but high levels of B₂O₃ compromise annealing point.

In addition to meltability and annealing point considerations, for AMLCDapplications, the CTE of the glass should be compatible with that ofsilicon. To achieve such CTE values, exemplary glasses can control theRO content of the glass. For a given Al₂O₃ content, controlling the ROcontent corresponds to controlling the RO/Al₂O₃ ratio. In practice,glasses having suitable CTE's are produced if the RO/Al₂O₃ ratio isbelow about 1.6.

On top of these considerations, the glasses are preferably formable by adowndraw process, e.g., a fusion process, which means that the glass'liquidus viscosity needs to be relatively high. Individual alkalineearths play an important role in this regard since they can destabilizethe crystalline phases that would otherwise form. BaO and SrO areparticularly effective in controlling the liquidus viscosity and areincluded in exemplary glasses for at least this purpose. As illustratedin the examples presented below, various combinations of the alkalineearths will produce glasses having high liquidus viscosities, with thetotal of the alkaline earths satisfying the RO/Al₂O₃ ratio constraintsneeded to achieve low melting temperatures, high annealing points, andsuitable CTE's. In some embodiments, the liquidus viscosity is greaterthan or equal to about 150 kP.

In addition to the above components, the glass compositions describedherein can include various other oxides to adjust various physical,melting, fining, and forming attributes of the glasses. Examples of suchother oxides include, but are not limited to, TiO₂, MnO, Fe₂O₃, ZnO,Nb₂O₅, MoO₃, Ta₂O₅, WO₃, Y₂O₃, La₂O₃ and CeO₂ as well as other rareearth oxides and phosphates. In one embodiment, the amount of each ofthese oxides can be less than or equal to 2.0 mole percent, and theirtotal combined concentration can be less than or equal to 5.0 molepercent. In some embodiments, the glass composition comprises ZnO in anamount in the range of about 0 to about 1.5 mol %, or about 0 to about1.0 mol %. The glass compositions described herein can also includevarious contaminants associated with batch materials and/or introducedinto the glass by the melting, fining, and/or forming equipment used toproduce the glass, particularly Fe₂O₂ and ZrO₂. The glasses can alsocontain SnO₂ either as a result of Joule melting using tin-oxideelectrodes and/or through the batching of tin containing materials,e.g., SnO₂, SnO, SnCO₃, SnC₂O₂, etc.

The glass compositions are generally alkali free; however, the glassescan contain some alkali contaminants. In the case of AMLCD applications,it is desirable to keep the alkali levels below 0.1 mole percent toavoid having a negative impact on thin film transistor (TFT) performancethrough diffusion of alkali ions from the glass into the silicon of theTFT. As used herein, an “alkali-free glass” is a glass having a totalalkali concentration which is less than or equal to 0.1 mole percent,where the total alkali concentration is the sum of the Na₂O, K₂O, andLi₂O concentrations. In one embodiment, the total alkali concentrationis less than or equal to 0.1 mole percent.

As discussed above, (MgO+CaO+SrO+BaO)/Al₂O₃ ratios greater than or equalto 1.0 improve fining, i.e., the removal of gaseous inclusions from themelted batch materials. This improvement allows for the use of moreenvironmentally friendly fining packages. For example, on an oxidebasis, the glass compositions described herein can have one or more orall of the following compositional characteristics: (i) an As₂O₃concentration of at most 0.05 mole percent; (ii) an Sb₂O₃ concentrationof at most 0.05 mole percent; (iii) a SnO₂ concentration of at most 0.25mole percent.

As₂O₃ is an effective high temperature fining agent for AMLCD glasses,and in some embodiments described herein, As₂O₃ is used for finingbecause of its superior fining properties. However, As₂O₃ is poisonousand requires special handling during the glass manufacturing process.Accordingly, in certain embodiments, fining is performed without the useof substantial amounts of As₂O₃, i.e., the finished glass has at most0.05 mole percent As₂O₃. In one embodiment, no As₂O₃ is purposely usedin the fining of the glass. In such cases, the finished glass willtypically have at most 0.005 mole percent As₂O₃ as a result ofcontaminants present in the batch materials and/or the equipment used tomelt the batch materials.

Although not as toxic as As₂O₃, Sb₂O₃ is also poisonous and requiresspecial handling. In addition, Sb₂O₃ raises the density, raises the CTE,and lowers the annealing point in comparison to glasses that use As₂O₃or SnO₂ as a fining agent. Accordingly, in certain embodiments, finingis performed without the use of substantial amounts of Sb₂O₃, i.e., thefinished glass has at most 0.05 mole percent Sb₂O₃. In anotherembodiment, no Sb₂O₃ is purposely used in the fining of the glass. Insuch cases, the finished glass will typically have at most 0.005 molepercent Sb₂O₃ as a result of contaminants present in the batch materialsand/or the equipment used to melt the batch materials.

Compared to As₂O₃ and Sb₂O₃ fining, tin fining (i.e., SnO₂ fining) isless effective, but SnO₂ is a ubiquitous material that has no knownhazardous properties. Also, for many years, SnO₂ has been a component ofAMLCD glasses through the use of tin oxide electrodes in the Joulemelting of the batch materials for such glasses. The presence of SnO₂ inAMLCD glasses has not resulted in any known adverse effects in the useof these glasses in the manufacture of liquid crystal displays. However,high concentrations of SnO₂ are not preferred as this can result in theformation of crystalline defects in AMLCD glasses. In one embodiment,the concentration of SnO₂ in the finished glass is less than or equal to0.25 mole percent.

In some embodiments, it was unexpectedly discovered that higherviscosity glasses described herein can allow a higher concentration ofSnO₂ without resulting in any deleterious effects to the glass. Forexample, conventional wisdom would inform one that a glass having a highannealing point results in a high melting temperature. Such high meltingtemperatures can result in a worse inclusion quality in the respectiveglass. To address such inclusion quality, finers can be added; however,glasses having a low viscosity generally do not permit the addition ofSnO₂ due to crystallization thereof in the glass. Exemplary glasses, asdescribed herein, however, can possess a higher viscosity resulting inhigher forming temperatures and thus allowing a greater concentration offining agent to be added to the glass thereby resulting in lessinclusions. Simply put, it was discovered that by varying thecomposition of an exemplary glass to create a higher processtemperature, a greater amount of fining agent could be added to removeinclusions before crystallization occurred. Thus, an exemplary glass caninclude SnO₂ at a concentration of between 0.001 mol % and 0.5 mol % anda T_(35kP) greater than or equal to about 1270° C., greater than orequal to about 1280° C., or greater than or equal to about 1290° C.Another exemplary glass can include SnO₂ at a concentration of between0.001 mol % and 0.5 mol % and a T_(200P) greater than or equal to about1650° C., greater than or equal to about 1660° C., or greater than orequal to about 1670° C. Another exemplary glass can include SnO₂ at aconcentration of between 0.001 mol % and 0.5 mol % and a T_(35kP)greater than or equal to about 1270° C., greater than or equal to about1280° C., or greater than or equal to about 1290° C. as well as aT_(200P) greater than or equal to about 1650° C., greater than or equalto about 1660° C., or greater than or equal to about 1670° C. Furtherexemplary glasses can include SnO₂ at a concentration of between 0.001mol % and 0.5 mol % and a liquidus temperature of greater than about1150° C., greater than about 1165° C., or greater than about 1170° C.Such a glass can also have T_(35kP) and/or T_(200P) as discussed above.Of course, SnO₂ can be provided to the glass as a result of Joulemelting using tin-oxide electrodes and/or through the batching of tincontaining materials, e.g., SnO₂, SnO, SnCO₃, SnC₂O₂, etc.

Tin fining can be used alone or in combination with other finingtechniques if desired. For example, tin fining can be combined withhalide fining, e.g., bromine fining. Other possible combinationsinclude, but are not limited to, tin fining plus sulfate, sulfide,cerium oxide, mechanical bubbling, and/or vacuum fining. It iscontemplated that these other fining techniques can be used alone. Incertain embodiments, maintaining the (MgO+CaO+SrO+BaO)/Al₂O₃ ratio andindividual alkaline earth concentrations within the ranges discussedabove makes the fining process easier to perform and more effective.

The glasses described herein can be manufactured using varioustechniques known in the art. In one embodiment, the glasses are madeusing a downdraw process such as, for example, a fusion downdrawprocess. In one embodiment, described herein is a method for producingan alkali-free glass sheet by a downdraw process comprising selecting,melting, and fining batch materials so that the glass making up thesheets comprises SiO₂, Al₂O₃, B₂O₃, MgO, CaO and BaO, and, on an oxidebasis, comprises: (i) a (MgO+CaO+SrO+BaO)/Al₂O₃ ratio greater than orequal to 1.0; (ii) a MgO content greater than or equal to 3.0 molepercent; (iii) a CaO content greater than or equal to 4.0 mole percent;and (iv) a BaO content greater than or equal to 1.0 mole percent,wherein: (a) the fining is performed without the use of substantialamounts of arsenic (and, optionally, without the use of substantialamounts of antimony); and (b) a population of 50 sequential glass sheetsproduced by the downdraw process from the melted and fined batchmaterials has an average gaseous inclusion level of less than 0.10gaseous inclusions/cubic centimeter, where each sheet in the populationhas a volume of at least 500 cubic centimeters.

U.S. Pat. No. 5,785,726 (Dorfeld et al.), U.S. Pat. No. 6,128,924 (Bangeet al.), U.S. Pat. No. 5,824,127 (Bange et al.), and U.S. Pat. Nos.7,628,038 and 7,628,039 (De Angelis, et al.) disclose processes formanufacturing arsenic free glasses. U.S. Pat. No. 7,696,113 (Ellison)discloses a process for manufacturing arsenic- and antimony-free glassusing iron and tin to minimize gaseous inclusions.

According to one embodiment, a population of 50 sequential glass sheetsproduced by the downdraw process from the melted and fined batchmaterials has an average gaseous inclusion level of less than 0.05gaseous inclusions/cubic centimeter, where each sheet in the populationhas a volume of at least 500 cubic centimeters.

The etch rate of the glass composition is a measure of how quickly amaterial can be removed from the glass and a rapid etch rate has beenfound to provide value to panel makers. The inventors have identified an“etch index” which allows one to estimate the etch rate of a glasscomposition in commercially relevant etching processes (such as, but notlimited to, a ten minute soak in a 10% HF/5% HCl solution at 30° C.).This etch index is defined by equation (2)Etchindex=−54.6147+(2.50004)*(Al₂O₃)+(1.3134)*(B₂O₃)+(1.84106)*(MgO)+(3.01223)*(CaO)+(3.7248)*(SrO)+(4.13149)*(BaO)  (2)where the oxides are in mol %. In some embodiments, the etch index isgreater than or equal to about 21. In various embodiments, the etchindex is greater than or equal to about 21.5, 22, 22.5, 23, 23.5, 24,24.5, 25, 25.5, 26, 26.5, 27, 27.5, 28, 28.5, 29, 29.5, 30, 30.5 or 31.

Some embodiments of the present disclosure are directed to a glasscomposition comprising, in mol % on an oxide basis in the ranges:

-   -   SiO₂ 68.5-72.0    -   Al₂O₃≥13.0    -   B₂O₃≤2.5    -   MgO 1.0-6.0    -   CaO 4.0-8.0    -   SrO≤4.5    -   BaO≤4.5        wherein        1.0≤(MgO+CaO+SrO+BaO)/Al₂O₃≤1.6,

an etch index ≥21;

an annealing point ≥800° C.; and

a Modulus >82 GPa.

One or more embodiments of the present disclosure is directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 63.0-71.0    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-3.0    -   MgO 0.9-9.0    -   CaO 5.25-6.5    -   SrO>0-6.0    -   BaO 1.0-9.0.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 68.0-71.0    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-2.0    -   MgO 3.5-5.0    -   CaO 5.25-6.5    -   SrO>0-2.0    -   BaO 2.5-4.5.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 68.0-70.5    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-3.0    -   MgO 0.9-9.0    -   CaO 5.25-11    -   SrO>0-6.0    -   BaO 1.0-9.0.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 68.0-70.5    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-2.0    -   MgO 3.5-5.0    -   CaO 5.25-10.0    -   SrO>0-2.0    -   BaO 2.5-4.5.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 63.0-75.0    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-2.8    -   MgO 0.9-9.0    -   CaO 5.25-11    -   SrO>0-6.0    -   BaO 1.0-9.0.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 68.0-72.0    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-2.0    -   MgO 3.5-5.0    -   CaO 5.25-10.0    -   SrO>0-2.0    -   BaO 2.5-4.5.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 63.0-75.0    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-3.0    -   MgO 0.9-9.0    -   CaO 5.25-11    -   SrO>0-6.0    -   BaO 3.0-5.4.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 68.0-72.0    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-2.0    -   MgO 3.5-5.0    -   CaO 5.25-10.0    -   SrO>0-2.0    -   BaO 2.5-4.5.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 63.0-75.0    -   Al₂O₃ 13.0-14.5    -   B₂O₃>0-2.0    -   MgO 0.9-9.0    -   CaO 5.0-6.5    -   SrO>0-6.0    -   BaO 1.0-9.0,        having (MgO+CaO+SrO+BaO)/Al₂O₃ 1.1-1.6

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 68.0-72.0    -   Al₂O₃ 13.0-14.5    -   B₂O₃>0-2.0    -   MgO 3.5-5.0    -   CaO 5.25-6.5    -   SrO>0-2.0    -   BaO 2.5-4.5.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 63.0-71.0    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-2.0    -   MgO 0.9-9.0    -   CaO 5.25-6.5    -   SrO>0-6.0    -   BaO 1.0-9.0.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 68.0-71.0    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-2.0    -   MgO 3.5-5.0    -   CaO 5.25-6.5    -   SrO>0-2.0    -   BaO 2.5-4.5.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 63.0-71.0    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-2.0    -   MgO 0.9-9.0    -   CaO 5.0-6.5    -   SrO>0-6.0    -   BaO 3.5-4.0.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 68.0-71.0    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-2.0    -   MgO 3.5-5.0    -   CaO 5.0-6.5    -   SrO>0-2.0    -   BaO 3.5-4.0.

Some embodiments of the present disclosure are directed to asubstantially alkali free glass comprising, in mole percent on an oxidebasis in the ranges:

-   -   SiO₂ 63.0-71.0    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-2.0    -   MgO 0.9-9.0    -   CaO 5.0-6.5    -   SrO>0-6.0    -   BaO 1.0-9.0,        wherein the sum of CaO and BaO>8.6.

Some embodiments of the present disclosure are directed to glasscomprising, in mole percent on an oxide basis in the ranges:

-   -   SiO₂ 68.0-71.0    -   Al₂O₃ 13.0-14.0    -   B₂O₃>0-2.0    -   MgO 3.5-5.0    -   CaO 5.0-6.5    -   SrO>0-2.0    -   BaO 2.5-4.5.

One or more embodiments of the present disclosure are directed tosubstantially alkali free glass having an annealing temperature greaterthan or equal to about 785° C.; a density less than or equal to about2.65 g/cc; a T_(200P) less than or equal to about 1750° C.; a T_(35kP)less than or equal to about 1340° C.; a Young's modulus greater than orequal to about 82 GPa; and an etch index in 10% HF/HCl greater than orequal to about 17.3 μm/mm³. In a detailed embodiment, the glass has anannealing temperature greater than or equal to about 800° C.; a densityless than or equal to about 2.61 g/cc; a T_(200P) less than or equal toabout 1700° C.; a T_(35kP) less than or equal to about 1310° C.; and anetch index greater than or equal to about 18.5 μm/mm³. In someembodiments, the glass article has a T_(200P) less than or equal toabout 1740° C., or 1730° C., or 1720° C., or 1710° C., or 1700° C., or1690° C., 1680° C., 1670° C., 1660° C. or 1650° C. In one or moreembodiments, the glass article has a T_(200P) in the range of about1640° C. to about 1705° C., or in the range of about 1646° C. to about1702° C., or in the range of about 1650° C. to about 1700° C.

One or more embodiments of the present disclosure are directed tosubstantially alkali free glass having one or more of: an annealingtemperature greater than or equal to about 785° C.; a density less thanor equal to about 2.65 g/cc; a T_(200P) less than or equal to about1750° C.; a T_(35kP) less than or equal to about 1340° C.; a Young'smodulus greater than or equal to about 82 GPa; or an etch index in 10%HF/HCl greater than or equal to about 17.3 μm/mm³. In some embodiments,the glass has one or more of: an annealing temperature greater than orequal to about 800° C.; a density less than or equal to about 2.61 g/cc;a T_(200P) less than or equal to about 1700° C.; a T_(35kP) less than orequal to about 1310° C.; or an etch index greater than or equal to about18.5 μm/mm³.

One or more embodiments of the disclosure are directed to glasssubstantially free of alkalis comprising in mol % on an oxide basis,

-   -   SiO₂ 69.76-71.62    -   Al₂O₃ 11.03-13.57    -   B₂O₃ 0-2.99    -   MgO 3.15-5.84    -   CaO 4.55-7.35    -   SrO 0.2-1.99    -   BaO 2.61-4.41    -   ZnO 0-1.0,        wherein the glass has a ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ is in        the range of about 1.0 and 1.6 and the ratio of        MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and 0.37. In        various embodiments, the glass has one or more of: a T(ann)>785°        C.; a density <2.65 g/cc; a T(_(200P))<1750° C.; a        T(_(35kP))<1340° C.; a Young's modulus >82 GPa; or an etch index        >21.

Some embodiments of the disclosure are directed to glass substantiallyfree of alkalis comprising in mol % on an oxide basis,

-   -   SiO₂ 68.14-72.29    -   Al₂O₃ 11.03-14.18    -   B₂O₃ 0-2.99    -   MgO 1.09-7.2    -   CaO 4.12-9.97    -   SrO 0.2-4.15    -   BaO 1.26-4.41    -   ZnO 0-1.0,        wherein the ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of        about 1.0 and 1.6 and the ratio of MgO/(MgO+CaO+SrO+BaO) is in        the range of about 0.22 and 0.37. In various embodiments, the        glass has one or more of: a T(ann)>785° C.; a density <2.65        g/cc; a T(_(200P))<1750° C.; a T(_(35kP))<1340° C.; a Young's        modulus >82 GPa; or an etch index >21 μm/mm³.

One or more embodiments of the disclosure are directed to substantiallyalkali free glass wherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range ofabout 1.0 and 1.6, the ratio of MgO/(MgO+CaO+SrO+BaO) is in the range ofabout 0.22 and 0.37. In some embodiments, the glass has one or more of′T(ann)>785° C., density <2.65 g/cc, T(200P)<1750° C., T(35 kP)<1340° C.,Young's modulus >82 GPa, or an etch index >21 μm/mm³. In variousembodiments, the glass comprises, in mol % on an oxide basis, one ormore of: SiO₂ in the range 68.14-72.29; Al₂O₃ in the range 11.03-14.18;B₂O₃ in the range 0-2.99; MgO in the range 1.09-7.2; CaO in the range4.12-9.97; SrO in the range 0.2-4.15; BaO in the range 1.26-4.41; and/orZnO in the range 0-1.0.

Some embodiments are directed to a substantially alkali free glasswherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and 1.6,the ratio of MgO/(MgO+CaO+SrO+BaO) is in the range of about 0.22 and0.37 and the glass has a liquidus viscosity >150 kP. In variousembodiments, the glass comprises, in mol % on an oxide basis, one ormore of: SiO₂ in the range 68.14-72.29; Al₂O₃ in the range 11.03-14.18;B₂O₃ in the range 0-2.99; MgO in the range 1.09-7.2; CaO in the range4.12-9.97; SrO in the range 0.2-4.15; BaO in the range 1.26-4.41; and/orZnO in the range 0-1.0.

One or more embodiments are directed to substantially alkali free glasswherein (MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of about 1.0 and about1.6, and the glass has an etch index greater than or equal to 23 μm/mm³,a T(ann)>800° C. and Young's modulus >82 GPa. In various embodiments,the glass comprises, in mol % on an oxide basis, one or more of: SiO₂ inthe range 68.14-72.29; Al₂O₃ in the range 11.03-14.18; B₂O₃ in the range0-2.99; MgO in the range 1.09-7.2; CaO in the range 4.12-9.97; SrO inthe range 0.2-4.15; BaO in the range 1.26-4.41; and/or ZnO in the range0-1.0.

Some embodiments of the disclosure are directed to aluminosilicate glassarticles that are substantially free of alkalis, wherein the glassarticle has an annealing temperature greater than or equal to about 795°C.; a density less than or equal to about 2.63 g/cc; a T_(200P) lessthan or equal to about 1730° C.; a T_(35kP) less than or equal to about1320° C.; a Young's modulus greater than or equal to about 81.5 GPa; andan etch index greater than or equal to about 23 μm/mm³. In variousembodiments, the aluminosilicate glass article comprises one or more of:SiO₂ in the range of 68.5-72 mol %; greater than or equal to 13 mol %Al₂O₃; B₂O₃ in the range of 0-2.5 mol %; MgO in the range of 1-6 mol %;CaO in the range of 4-8 mol %; SrO in the range 0-4.5 mol %; BaO in therange 0-4.5 mol %; and/or a ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ in therange of 1-1.6.

Some embodiments of the disclosure are directed to an aluminosilicateglass article that is substantially free of alkalis, wherein the glassarticle has:an annealing temperature greater than or equal to about 800°C.; a density less than or equal to about 2.61 g/cc; a T_(200P) lessthan or equal to about 1710° C.; a T_(35kP) less than or equal to about1310° C.; a Young's modulus greater than or equal to about 81.2 GPa; andan etch index greater than or equal to about 23 μm/mm³. In variousembodiments, the aluminosilicate glass article comprises one or more of:SiO₂ in the range of 68.5-72 mol %; greater than or equal to 13 mol %Al₂O₃; B₂O₃ in the range of 0-2.5 mol %; MgO in the range of 1-6 mol %;CaO in the range of 4-8 mol %; SrO in the range 0-4.5 mol %; BaO in therange 0-4.5 mol %; and/or a ratio of (MgO+CaO+SrO+BaO)/Al₂O₃ in therange of 1-1.6.

It will be appreciated that the various disclosed embodiments mayinvolve particular features, elements or steps that are described inconnection with that particular embodiment. It will also be appreciatedthat a particular feature, element or step, although described inrelation to one particular embodiment, may be interchanged or combinedwith alternate embodiments in various non-illustrated combinations orpermutations.

It is also to be understood that, as used herein the terms “the,” “a,”or “an,” mean “at least one,” and should not be limited to “only one”unless explicitly indicated to the contrary.

Ranges can be expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, examples include from the one particular value and/or to theother particular value. Similarly, when values are expressed asapproximations, by use of the antecedent “about,” it will be understoodthat the particular value forms another aspect. It will be furtherunderstood that the endpoints of each of the ranges are significant bothin relation to the other endpoint, and independently of the otherendpoint.

The terms “substantial,” “substantially,” and variations thereof as usedherein are intended to note that a described feature is equal orapproximately equal to a value or description. Moreover, “substantiallysimilar” is intended to denote that two values are equal orapproximately equal. In some embodiments, “substantially similar” maydenote values within about 10% of each other, such as within about 5% ofeach other, or within about 2% of each other.

Unless otherwise expressly stated, it is in no way intended that anymethod set forth herein be construed as requiring that its steps beperformed in a specific order. Accordingly, where a method claim doesnot actually recite an order to be followed by its steps or it is nototherwise specifically stated in the claims or descriptions that thesteps are to be limited to a specific order, it is no way intended thatany particular order be inferred.

While various features, elements or steps of particular embodiments maybe disclosed using the transitional phrase “comprising,” it is to beunderstood that alternative embodiments, including those that may bedescribed using the transitional phrases “consisting” or “consistingessentially of,” are implied. Thus, for example, implied alternativeembodiments to an apparatus that comprises A+B+C include embodimentswhere an apparatus consists of A+B+C and embodiments where an apparatusconsists essentially of A+B+C.

It will be apparent to those skilled in the art that variousmodifications and variations can be made to the present disclosurewithout departing from the spirit and scope of the disclosure. Sincemodifications combinations, sub-combinations and variations of thedisclosed embodiments incorporating the spirit and substance of thedisclosure may occur to persons skilled in the art, the disclosureshould be construed to include everything within the scope of theappended claims and their equivalents.

EXAMPLES

The following examples are set forth below to illustrate the methods andresults according to the disclosed subject matter. These examples arenot intended to be inclusive of all embodiments of the subject matterdisclosed herein, but rather to illustrate representative methods andresults. These examples are not intended to exclude equivalents andvariations of the present disclosure which are apparent to one skilledin the art.

Efforts have been made to ensure accuracy with respect to numbers (e.g.,amounts, temperature, etc.) but some errors and deviations should beaccounted for. Unless indicated otherwise, temperature is in ° C. or isat ambient temperature, and pressure is at or near atmospheric. Thecompositions themselves are given in mole percent on an oxide basis andhave been normalized to 100%. There are numerous variations andcombinations of reaction conditions, e.g., component concentrations,temperatures, pressures and other reaction ranges and conditions thatcan be used to optimize the product purity and yield obtained from thedescribed process. Only reasonable and routine experimentation will berequired to optimize such process conditions.

The glass properties set forth in Table 1 were determined in accordancewith techniques conventional in the glass art. Thus, the linearcoefficient of thermal expansion (CTE) over the temperature range25-300° C. is expressed in terms of ×10⁻⁷/° C. and the annealing pointis expressed in terms of ° C. These were determined from fiberelongation techniques (ASTM references E228-85 and C336, respectively).The density in terms of grams/cm³ was measured via the Archimedes method(ASTM C693). The melting temperature in terms of ° C. (defined as thetemperature at which the glass melt demonstrates a viscosity of 200poises) was calculated employing a Fulcher equation fit to hightemperature viscosity data measured via rotating cylinders viscometry(ASTM C965-81).

The liquidus temperature of the glass in terms of ° C. was measuredusing the standard gradient boat liquidus method of ASTM C829-81. Thisinvolves placing crushed glass particles in a platinum boat, placing theboat in a furnace having a region of gradient temperatures, heating theboat in an appropriate temperature region for 24 hours, and determiningby means of microscopic examination the highest temperature at whichcrystals appear in the interior of the glass. More particularly, theglass sample is removed from the Pt boat in one piece, and examinedusing polarized light microscopy to identify the location and nature ofcrystals which have formed against the Pt and air interfaces, and in theinterior of the sample. Because the gradient of the furnace is very wellknown, temperature vs. location can be well estimated, within 5-10° C.The temperature at which crystals are observed in the internal portionof the sample is taken to represent the liquidus of the glass (for thecorresponding test period). Testing is sometimes carried out at longertimes (e.g. 72 hours), to observe slower growing phases. The liquidusviscosity in poises was determined from the liquidus temperature and thecoefficients of the Fulcher equation.

Young's modulus values in terms of GPa were determined using a resonantultrasonic spectroscopy technique of the general type set forth in ASTME1875-00e1.

Exemplary glasses are shown in Table 1. As can be seen in Table 1, theexemplary glasses have density, annealing point and Young's modulusvalues that make the glasses suitable for display applications, such asAMLCD substrate applications, and more particularly for low-temperaturepolysilicon and oxide thin film transistor applications. Although notshown in Table 1, the glasses have durabilities in acid and base mediathat are similar to those obtained from commercial AMLCD substrates, andthus are appropriate for AMLCD applications. The exemplary glasses canbe formed using downdraw techniques, and in particular are compatiblewith the fusion process, via the aforementioned criteria.

The exemplary glasses of Table 1 were prepared using a commercial sandas a silica source, milled such that 90% by weight passed through astandard U.S. 100 mesh sieve. Alumina was the alumina source, periclasewas the source for MgO, limestone the source for CaO, strontiumcarbonate, strontium nitrate or a mix thereof was the source for SrO,barium carbonate was the source for BaO, and tin (IV) oxide was thesource for SnO₂. The raw materials were thoroughly mixed, loaded into aplatinum vessel suspended in a furnace heated by silicon carbideglowbars, melted and stirred for several hours at temperatures between1600 and 1650° C. to ensure homogeneity, and delivered through anorifice at the base of the platinum vessel. The resulting patties ofglass were annealed at or near the annealing point, and then subjectedto various experimental methods to determine physical, viscous andliquidus attributes.

These methods are not unique, and the glasses of Table 1 can be preparedusing standard methods well-known to those skilled in the art. Suchmethods include a continuous melting process, such as would be performedin a continuous melting process, wherein the melter used in thecontinuous melting process is heated by gas, by electric power, orcombinations thereof.

Raw materials appropriate for producing exemplary glasses includecommercially available sands as sources for SiO₂; alumina, aluminumhydroxide, hydrated forms of alumina, and various aluminosilicates,nitrates and halides as sources for Al₂O₃; boric acid, anhydrous boricacid and boric oxide as sources for B₂O₃; periclase, dolomite (also asource of CaO), magnesia, magnesium carbonate, magnesium hydroxide, andvarious forms of magnesium silicates, aluminosilicates, nitrates andhalides as sources for MgO; limestone, aragonite, dolomite (also asource of MgO), wolastonite, and various forms of calcium silicates,aluminosilicates, nitrates and halides as sources for CaO; and oxides,carbonates, nitrates and halides of strontium and barium. If a chemicalfining agent is desired, tin can be added as SnO₂, as a mixed oxide withanother major glass component (e.g., CaSnO₃), or in oxidizing conditionsas SnO, tin oxalate, tin halide, or other compounds of tin known tothose skilled in the art.

The glasses in Table 1 contain SnO₂ as a fining agent, but otherchemical fining agents could also be employed to obtain glass ofsufficient quality for TFT substrate applications. For example,exemplary glasses could employ any one or combinations of As₂O₃, Sb₂O₃,CeO₂, Fe₂O₃, and halides as deliberate additions to facilitate fining,and any of these could be used in conjunction with the SnO₂ chemicalfining agent shown in the examples. Of these, As₂O₃ and Sb₂O₃ aregenerally recognized as hazardous materials, subject to control in wastestreams such as might be generated in the course of glass manufacture orin the processing of TFT panels. It is therefore desirable to limit theconcentration of As₂O₃ and Sb₂O₃ individually or in combination to nomore than 0.005 mol %.

In addition to the elements deliberately incorporated into exemplaryglasses, nearly all stable elements in the periodic table are present inglasses at some level, either through low levels of contamination in theraw materials, through high-temperature erosion of refractories andprecious metals in the manufacturing process, or through deliberateintroduction at low levels to fine tune the attributes of the finalglass. For example, zirconium may be introduced as a contaminant viainteraction with zirconium-rich refractories. As a further example,platinum and rhodium may be introduced via interactions with preciousmetals. As a further example, iron may be introduced as a tramp in rawmaterials, or deliberately added to enhance control of gaseousinclusions. As a further example, manganese may be introduced to controlcolor or to enhance control of gaseous inclusions. As a further example,alkalis may be present as a tramp component at levels up to about 0.1mol % for the combined concentration of Li₂O, Na₂O and K₂O.

Hydrogen is inevitably present in the form of the hydroxyl anion, OH⁻,and its presence can be ascertained via standard infrared spectroscopytechniques. Dissolved hydroxyl ions significantly and nonlinearly impactthe annealing point of exemplary glasses, and thus to obtain the desiredannealing point it may be necessary to adjust the concentrations ofmajor oxide components so as to compensate. Hydroxyl ion concentrationcan be controlled to some extent through choice of raw materials orchoice of melting system. For example, boric acid is a major source ofhydroxyls, and replacing boric acid with boric oxide can be a usefulmeans to control hydroxyl concentration in the final glass. The samereasoning applies to other potential raw materials comprising hydroxylions, hydrates, or compounds comprising physisorbed or chemisorbed watermolecules. If burners are used in the melting process, then hydroxylions can also be introduced through the combustion products fromcombustion of natural gas and related hydrocarbons, and thus it may bedesirable to shift the energy used in melting from burners to electrodesto compensate. Alternatively, one might instead employ an iterativeprocess of adjusting major oxide components so as to compensate for thedeleterious impact of dissolved hydroxyl ions.

Sulfur is often present in natural gas, and likewise is a trampcomponent in many carbonate, nitrate, halide, and oxide raw materials.In the form of SO₂, sulfur can be a troublesome source of gaseousinclusions. The tendency to form SO₂-rich defects can be managed to asignificant degree by controlling sulfur levels in the raw materials,and by incorporating low levels of comparatively reduced multivalentcations into the glass matrix. While not wishing to be bound by theory,it appears that SO₂-rich gaseous inclusions arise primarily throughreduction of sulfate (SO₄ ⁻) dissolved in the glass. The elevated bariumconcentrations of exemplary glasses appear to increase sulfur retentionin the glass in early stages of melting, but as noted above, barium isrequired to obtain low liquidus temperature, and hence highT_(35k)−T_(liq) and high liquidus viscosity. Deliberately controllingsulfur levels in raw materials to a low level is a useful means ofreducing dissolved sulfur (presumably as sulfate) in the glass. Inparticular, sulfur is preferably less than 200 ppm by weight in thebatch materials, and more preferably less than 100 ppm by weight in thebatch materials.

Reduced multivalents can also be used to control the tendency ofexemplary glasses to form SO₂ blisters. While not wishing to be bound totheory, these elements behave as potential electron donors that suppressthe electromotive force for sulfate reduction. Sulfate reduction can bewritten in terms of a half reaction such asSO₄ ⁻→SO₂+O₂+2e ⁻where e⁻ denotes an electron. The “equilibrium constant” for the halfreaction isK_(eq)=[SO₂][O₂ ][e ⁻]²/[SO₄ ⁻]where the brackets denote chemical activities. Ideally one would like toforce the reaction so as to create sulfate from SO₂, O₂ and 2e⁻. Addingnitrates, peroxides, or other oxygen-rich raw materials may help, butalso may work against sulfate reduction in the early stages of melting,which may counteract the benefits of adding them in the first place. SO₂has very low solubility in most glasses, and so is impractical to add tothe glass melting process. Electrons may be “added” through reducedmultivalents. For example, an appropriate electron-donating halfreaction for ferrous iron (Fe²⁺) is expressed as2Fe²⁺→2Fe³⁺+2e ⁻

This “activity” of electrons can force the sulfate reduction reaction tothe left, stabilizing SO₄ ⁻ in the glass. Suitable reduced multivalentsinclude, but are not limited to, Fe²⁺, Mn²⁺, Sn²⁺, Sb³⁺, As³⁺, Ti³⁺, andothers familiar to those skilled in the art. In each case, it may beimportant to minimize the concentrations of such components so as toavoid deleterious impact on color of the glass, or in the case of As andSb, to avoid adding such components at a high enough level so as tocomplication of waste management in an end-user's process.

In addition to the major oxides components of exemplary glasses, and theminor or tramp constituents noted above, halides may be present atvarious levels, either as contaminants introduced through the choice ofraw materials, or as deliberate components used to eliminate gaseousinclusions in the glass. As a fining agent, halides may be incorporatedat a level of about 0.4 mol % or less, though it is generally desirableto use lower amounts if possible to avoid corrosion of off-gas handlingequipment. In some embodiments, the concentrations of individual halideelements are below about 200 ppm by weight for each individual halide,or below about 800 ppm by weight for the sum of all halide elements.

In addition to these major oxide components, minor and tramp components,multivalents and halide fining agents, it may be useful to incorporatelow concentrations of other colorless oxide components to achievedesired physical, optical or viscoelastic properties. Such oxidesinclude, but are not limited to, TiO₂, ZrO₂, HfO₂, Nb₂O₅, Ta₂O₅, MoO₃,WO₃, ZnO, In₂O₃, Ga₂O₃, Bi₂O₃, GeO₂, PbO, SeO₃, TeO₂, Y₂O₃, La₂O₃,Gd₂O₃, and others known to those skilled in the art. Through aniterative process of adjusting the relative proportions of the majoroxide components of exemplary glasses, such colorless oxides can beadded to a level of up to about 2 mol % without unacceptable impact toannealing point, T_(35k)−T_(liq) or liquidus viscosity.

Table 1 shows examples of glasses (samples 1-189) with a T(ann)>795° C.,a Young's modulus >81.5; and etch index >23, a density <2.63, aT(_(200P))<1730° C.; and a T(_(35kP))<1320° C. Table 2 shows additionalexamples (samples 190-426) of glasses that border the parameters ofTable 1.

TABLE 1 Sample 1 2 3 4 5 6 7 8 SiO₂ 69.99 70.3 70.45 70.84 70.32 70.770.56 70.57 Al₂O₃ 13.57 13.43 13.1 13.11 13.35 13.35 13.31 13.29 B₂O₃1.84 1.76 1.91 1.97 1.77 1.85 1.85 1.84 MgO 4.47 4.05 3.73 3.32 4.153.71 3.94 3.9 CaO 5.1 5.25 5.19 5.13 5.28 4.92 4.86 4.84 SrO 1.04 1.231.18 1.19 1.22 1.2 1.2 1.22 BaO 3.89 3.87 3.86 3.86 3.8 4.16 4.14 4.22ZnO 0 0 0.49 0.49 0 0 0 0 SnO₂ 0.09 0.08 0.07 0.07 0.08 0.1 0.09 0.09Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.01 0.01 0.010.02 0.01 0.02 0.02 RO/Al₂O₃ 1.07 1.07 1.07 1.03 1.08 1.05 1.06 1.07Annealing point 803.1 804.1 797.1 799.5 803.4 805.0 803.1 803.6 Young'smodulus 83.2 82.9 82.6 82.0 82.9 82.3 82.3 81.9 Etch index 25.3 25.124.1 23.3 24.9 24.5 24.6 24.8 Density 2.598 2.605 2.61 2.606 2.603 2.6012.609 2.61 T (200P) 1673 1681 1676 1687 1680 1695 1683 1686 T (35kP)1296 1300 1299 1304 1299 1307 1306 1307 T (liquidus) 1220 1200 1205 12301200 1200 1220 1210 Liquidus Viscosity 172156 299437 259980 160017293477 344633 215090 276815 Sample 9 10 11 12 13 14 15 16 SiO₂ 70.3870.49 69.72 70.59 70.8 70.83 70.83 70.82 Al₂O₃ 13.35 13.18 13.77 13.0213 13.17 13.2 13.2 B₂O₃ 1.72 1.67 1.56 1.63 1.65 1.7 1.75 1.79 MgO 4.154.23 2.87 4.36 4.05 3.81 3.73 3.69 CaO 5.27 5.25 6.51 5.22 5 4.93 4.94.89 SrO 1.23 1.22 2.27 1.22 1.23 1.22 1.22 1.22 BaO 3.81 3.84 3.2 3.854.15 4.23 4.26 4.27 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.09 0.07 0.09 0.1 0.10.1 0.1 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.010.01 0.01 0.02 0.02 0.01 0.01 RO/Al₂O₃ 1.08 1.10 1.08 1.13 1.11 1.081.07 1.07 Annealing point 801.0 803.4 807.7 802.5 803.1 804.6 804.1807.0 Young's modulus 82.9 82.9 83.3 82.9 82.4 82.3 82.2 82.1 Etch index24.9 24.5 28.4 24.3 24.3 24.4 24.5 24.4 Density 2.596 2.605 2.613 2.6052.612 2.603 2.61 2.603 T (200P) 1681 1683 1673 1683 1693 1697 1690 1698T (35kP) 1300 1300 1294 1300 1305 1308 1311 1308 T (liquidus) 1210 12101245 1200 1220 1200 1205 1195 Liquidus Viscosity 234831 236958 95668298562 206203 347978 335511 396996 Sample 17 18 19 20 21 22 23 24 SiO₂70.75 70.79 70.81 70.8 70.73 70.62 70.51 70.55 Al₂O₃ 13.25 13.28 13.2513.21 13.16 13.14 13.13 13.1 B₂O₃ 1.78 1.76 1.75 1.73 1.71 1.69 1.681.67 MgO 3.68 3.64 3.69 3.76 3.9 4.03 4.14 4.16 CaO 4.89 4.88 4.9 4.985.08 5.19 5.29 5.3 SrO 1.22 1.22 1.22 1.22 1.23 1.23 1.24 1.24 BaO 4.34.3 4.26 4.19 4.08 3.99 3.9 3.87 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.1 0.10.09 0.09 0.09 0.08 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01ZrO₂ 0.02 0.01 0.02 0.02 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.06 1.06 1.061.07 1.09 1.10 1.11 1.11 Annealing point 804.4 805.1 804.9 804.6 803.9806.0 802.7 802.8 Young's modulus 82.2 82.2 82.2 82.3 82.4 82.6 82.882.8 Etch index 24.7 24.6 24.5 24.5 24.5 24.6 24.7 24.6 Density 2.6142.613 2.612 2.61 2.609 2.598 2.606 2.597 T (200P) 1697 1699 1698 16961692 1688 1684 1684 T (35kP) 1308 1309 1309 1307 1305 1303 1300 1301 T(liquidus) 1190 1215 1210 1210 1205 1220 1205 1215 Liquidus Viscosity446666 250286 279227 272947 293653 196863 266563 211488 Sample 25 26 2728 29 30 31 32 SiO₂ 70.65 70.66 70.61 70.62 70.73 70.42 70.29 70.25Al₂O₃ 13.09 13.07 13.12 13.12 13.05 13.3 13.38 13.38 B₂O₃ 1.67 1.66 1.651.69 1.62 1.89 2.01 2.06 MgO 4.12 4.12 4.14 4.12 4.14 4.14 4.1 4.1 CaO5.3 5.3 5.31 5.3 5.3 5.03 5 5 SrO 1.24 1.24 1.24 1.24 1.23 1.12 1.121.11 BaO 3.84 3.85 3.82 3.81 3.83 3.99 3.99 3.99 ZnO 0 0 0 0 0 0 0 0SnO₂ 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 Fe₂O₃ 0.01 0.01 0.01 0.010.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0.02 0.01 0.01 0.01 0.01 0.01RO/Al₂O₃ 1.11 1.11 1.11 1.10 1.11 1.07 1.06 1.06 Annealing point 803.1804.0 803.5 803.2 803.6 802.3 801.4 800.8 Young's modulus 82.7 82.7 82.882.7 82.8 82.6 82.5 82.5 Etch index 24.3 24.3 24.4 24.3 24.1 24.5 24.724.8 Density 2.603 2.597 2.603 2.602 2.603 2.603 2.603 2.602 T (200P)1686 1686 1685 1685 1687 1684 1682 1682 T (35kP) 1302 1302 1301 13011302 1301 1300 1299 T (liquidus) 1230 1225 1200 1215 1205 1215 1215 1220Liquidus Viscosity 153437 172226 307133 215283 278162 213109 208030182951 Sample 33 34 35 36 37 38 39 40 SiO₂ 70.26 70.22 70.28 70.57 70.3670.34 70.54 70.77 Al₂O₃ 13.39 13.41 13.41 13.16 13.3 13.34 13.14 13.02B₂O₃ 2.01 2.05 2 2.06 2.13 2.1 1.93 1.69 MgO 4.12 4.09 4.09 3.82 3.863.88 3.84 3.86 CaO 5 5.01 5 4.87 5.14 5.18 5.18 5.17 SrO 1.12 1.12 1.121.54 1.25 1.2 1.41 1.53 BaO 3.99 4 4 3.9 3.88 3.88 3.87 3.88 ZnO 0 0 0 00 0 0 0 SnO₂ 0.08 0.08 0.08 0.06 0.06 0.06 0.06 0.06 Fe₂O₃ 0.01 0.010.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.02 0.01 0.01 0.01 0.010.01 RO/Al₂O₃ 1.06 1.06 1.06 1.07 1.06 1.06 1.09 1.11 Annealing point801.4 801.0 804.0 801.4 802.6 803.0 804.0 805.0 Young's modulus 82.582.5 82.5 82.1 82.4 82.3 82.3 82.4 Etch index 24.8 24.9 24.8 24.5 24.724.7 24.7 24.6 Density 2.603 2.603 2.596 2.603 2.6 2.597 2.604 2.606 T(200P) 1682 1681 1682 1690 1689 1683 1687 1691 T (35kP) 1299 1299 13001309 1302 1300 1301 1304 T (liquidus) 1230 1225 1225 1210 1230 1240 12251235 Liquidus Viscosity 146787 162568 165694 284226 154129 117760 170012143202 Sample 41 42 43 44 45 46 47 48 SiO₂ 70.59 70.72 70.53 70.7 70.4970.49 70.41 70.66 Al₂O₃ 13.36 13.33 13.3 13.38 13.26 13.31 13.32 13.21B₂O₃ 1.75 1.75 1.78 1.64 1.91 1.81 1.79 1.55 MgO 3.88 3.87 3.85 3.863.92 4.02 4.13 4.1 CaO 5.2 5.18 5.17 5.2 5.2 5.17 5.19 6.7 SrO 1.23 1.21.44 1.24 1.52 1.5 1.35 0.95 BaO 3.89 3.86 3.85 3.88 3.61 3.61 3.72 2.73ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.06 0.06 0.06 0.06 0.06 0.06 0.06 0.08 Fe₂O₃0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.010.01 0.01 0.02 RO/Al₂O₃ 1.06 1.06 1.08 1.06 1.07 1.07 1.08 1.10Annealing point 805.8 806.2 804.8 807.9 804.1 804.7 804.1 805.1 Young'smodulus 82.3 82.6 82.5 82.3 82.6 82.8 82.8 83.6 Etch index 24.5 24.224.9 24.4 24.5 24.5 24.7 23.0 Density 2.602 2.6 2.606 2.602 2.6 2.62.599 2.57 T (200P) 1686 1689 1678 1687 1669 1676 1679 1669 T (35kP)1305 1306 1302 1307 1293 1301 1300 1298 T (liquidus) 1220 1215 1215 12201235 1230 1230 1190 Liquidus Viscosity 210823 238881 223829 218427116321 153167 151713 383483 Sample 49 50 51 52 53 54 55 56 SiO₂ 71.1269.59 70.33 69.56 69.31 69.84 69.51 69.57 Al₂O₃ 13.39 13.83 13.43 13.8513.97 13.85 13.83 13.99 B₂O₃ 0.75 1.9 1.75 2.04 1.72 1.74 2 1.91 MgO3.56 2.76 4 2.72 2.72 2.68 2.55 2.51 CaO 7.45 6.26 5.21 6.18 7.45 6.267.4 6.75 SrO 1.13 1.38 1.23 1.35 0.62 1.56 0.7 1.31 BaO 2.48 4.19 3.934.19 4.1 3.96 3.92 3.86 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.09 0.070.07 0.07 0.07 0.07 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.09 1.05 1.07 1.041.07 1.04 1.05 1.03 Annealing point 818.3 803.2 804.4 807.1 809.2 807.3808.2 809.0 Young's modulus 84.4 82.4 82.8 82.9 83.6 82.3 82.7 82.3 Etchindex 23.3 28.8 25.1 28.7 29.3 28.3 28.4 28.7 Density 2.575 2.626 2.6072.614 2.62 2.624 2.611 2.616 T (200P) 1677 1673 1683 1678 1670 1673 16771682 T (35kP) 1309 1295 1301 1301 1298 1303 1300 1301 T (liquidus) >12701200 >1290 >1270 1250 1265 1260 Liquidus Viscosity 305275 105407 7067480473 Sample 57 58 59 60 61 62 63 64 SiO₂ 70.62 70.66 69.29 69.75 69.6169.21 69.76 69.75 Al₂O₃ 13.32 13.3 13.98 13.82 13.96 14.06 13.75 13.84B₂O₃ 1.82 1.79 1.77 1.56 1.58 1.69 1.85 1.83 MgO 3.84 3.82 3.78 2.582.41 2.64 2.16 2.1 CaO 5.17 5.16 5.48 6.36 7.27 6.38 7.11 6.41 SrO 1.521.62 2.01 2.35 1.61 3.06 2.5 3.25 BaO 3.62 3.56 3.61 3.48 3.45 2.86 2.772.73 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.06 0.06 0.07 0.07 0.07 0.07 0.07 0.07Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.010.01 0.01 0.01 0.01 RO/Al₂O₃ 1.06 1.06 1.06 1.07 1.06 1.06 1.06 1.05Annealing point 804.1 804.0 804.4 810.7 809.6 808.7 808.9 808.8 Young'smodulus 82.7 82.6 83.0 82.9 83.0 83.2 82.5 82.5 Etch index 24.3 24.328.5 29.0 28.9 30.0 28.3 28.9 Density 2.599 2.6 2.621 2.623 2.615 2.6222.603 2.614 T (200P) 1680 1679 1671 1670 1672 1672 1667 1679 T (35kP)1302 1302 1293 1301 1298 1293 1295 1301 T (liquidus) 1215 1235 1240 12801270 1235 1230 >1295 Liquidus Viscosity 222583 140296 104063 52848 62035114644 136873 Sample 65 66 67 68 69 70 71 72 SiO₂ 70.72 70.72 69.1169.51 69.91 70.02 70.41 69.89 Al₂O₃ 13.05 13.05 14.18 14.03 13.37 13.4613.29 13.96 B₂O₃ 1.66 1.65 1.77 1.69 1.62 1.7 1.3 1.32 MgO 4.12 4.122.14 2.16 3.21 2.91 3.45 2.81 CaO 5.29 5.29 6.86 5.94 6.58 6.62 6.316.01 SrO 1.23 1.23 3.14 4.15 2.13 2.2 2.02 2.85 BaO 3.83 3.82 2.71 2.423.07 2.99 3.12 3.07 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.07 0.07 0.070.06 0.07 0.07 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.010.03 0.01 0.01 0.02 0.01 0.01 0.01 RO/Al₂O₃ 1.11 1.11 1.05 1.05 1.121.09 1.12 1.06 Annealing point 803.3 806.0 810.5 812.1 801.1 806.0 807.0812.8 Young's modulus 82.7 82.7 82.7 83.2 82.7 82.6 83.8 83.3 Etch index24.1 24.1 30.7 30.0 27.3 27.1 26.1 28.6 Density 2.602 2.596 2.617 2.6212.603 2.602 2.606 2.623 T (200P) 1687 1687 1667 1677 1666 1680 1671 1687T (35kP) 1302 1303 1292 1299 1289 1295 1298 1302 T (liquidus) 1220 12201270 1280 1250 1260 1260 1250 Liquidus Viscosity 195363 196370 5410151305 76993 71088 75283 101098 Sample 73 74 75 76 77 78 79 80 SiO₂ 70.8169.63 70.49 70.38 70.49 70.81 70.91 70.23 Al₂O₃ 13.32 13.79 13.11 13.213.14 13.29 13.31 13.5 B₂O₃ 1.83 1.6 1.05 1.67 1.5 1.84 1.79 1.95 MgO3.57 3.11 4.12 3.31 3.86 3.62 3.54 3.16 CaO 4.88 5.95 5.99 6.16 5.774.87 4.86 6.27 SrO 1.23 2.82 1.81 1.92 1.65 1.23 1.23 0.93 BaO 4.23 33.33 3.25 3.48 4.21 4.22 3.87 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.07 0.080.08 0.08 0.1 0.1 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01ZrO₂ 0.02 0.01 0.01 0.01 0.01 0.02 0.02 0.01 RO/Al₂O₃ 1.04 1.08 1.161.11 1.12 1.05 1.04 1.05 Annealing point 805.2 808.0 808.1 805.5 804.9804.8 806.0 804.4 Young's modulus 82.1 82.7 83.1 82.5 83.5 82.1 82.182.0 Etch index 24.4 28.5 25.7 25.8 25.2 24.3 24.2 25.9 Density 2.612.618 2.607 2.603 2.602 2.609 2.609 2.6 T (200P) 1699 1676 1685 16771675 1699 1702 1679 T (35kP) 1309 1295 1299 1298 1295 1309 1311 1301 T(liquidus) 1200 1230 1250 1260 1230 1195 1200 1240 Liquidus Viscosity360371 134268 94961 74322 136577 403112 372425 123729 Sample 81 82 83 8485 86 87 88 SiO₂ 70.1 70.55 70.68 70.84 70.85 70.86 69.97 69.88 Al₂O₃13.57 13.26 13.18 13.59 13.44 13.44 13.35 13.35 B₂O₃ 2.01 1.65 1.64 1.431.56 1.59 1.63 1.74 MgO 3.06 3.61 3.69 2.3 3.07 3.25 5.1 5.21 CaO 6.45.92 5.83 6.43 6.17 6.09 5.05 4.96 SrO 0.83 1.28 1.36 2.19 0.78 0.451.29 1.24 BaO 3.94 3.62 3.53 3.12 4.02 4.23 3.5 3.51 ZnO 0 0 0 0 0 0 0 0SnO₂ 0.08 0.08 0.08 0.08 0.08 0.08 0.08 0.08 Fe₂O₃ 0.01 0.01 0.01 0.010.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0 0.01 0.01 RO/Al₂O₃1.05 1.09 1.09 1.03 1.04 1.04 1.12 1.12 Annealing point 805.3 806.1801.7 817.2 811.6 810.1 801.6 801.0 Young's modulus 82.3 83.0 82.7 82.782.5 82.0 83.1 83.8 Etch index 26.2 24.9 24.5 25.9 24.8 24.6 24.8 24.7Density 2.6 2.598 2.597 2.597 2.599 2.599 2.601 2.6 T (200P) 1680 16821681 1690 1694 1696 1660 1662 T (35kP) 1298 1302 1303 1314 1313 13131291 1290 T (liquidus) 1230 1230 1230 1270 1250 1230 1220 1220 LiquidusViscosity 143556 154047 158336 84630 125632 197745 156077 152568 Sample89 90 91 92 93 94 95 96 SiO₂ 69.84 69.89 69.87 69.83 69.87 69.91 70.169.91 Al₂O₃ 13.34 13.28 13.35 13.37 13.3 13.29 13.33 13.4 B₂O₃ 1.7 1.581.61 1.75 1.75 1.7 1.48 1.72 MgO 5.23 5.24 5.29 5.28 5.14 5.14 5.13 5.15CaO 5.05 5.16 5.11 4.98 5.14 5.15 5.01 4.96 SrO 1.09 1.08 0.92 0.94 0.920.95 1.12 0.97 BaO 3.64 3.66 3.73 3.73 3.76 3.74 3.72 3.79 ZnO 0 0 0 0 00 0 0 SnO₂ 0.09 0.09 0.09 0.09 0.09 0.08 0.09 0.09 Fe₂O₃ 0.01 0.01 0.010.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01RO/Al₂O₃ 1.13 1.14 1.13 1.12 1.12 1.13 1.12 1.11 Annealing point 802.0800.8 800.8 800.9 806.8 801.5 801.9 803.8 Young's modulus 83.9 83.6 83.884.3 83.7 83.2 83.4 83.4 Etch index 24.9 25.0 24.8 24.7 24.8 24.8 24.724.8 Density 2.602 2.604 2.603 2.602 2.602 2.604 2.601 2.602 T (200P)1669 1669 1661 1660 1669 1666 1678 1663 T (35kP) 1291 1291 1290 12891292 1292 1294 1291 T (liquidus) 1235 1220 1230 1225 1215 1225 1230 1230Liquidus Viscosity 111101 151913 123612 132943 177388 140726 129027125920 Sample 97 98 99 100 101 102 103 104 SiO₂ 69.77 69.72 69.71 69.8369.79 69.81 69.83 69.95 Al₂O₃ 13.4 13.29 13.35 13.33 13.34 13.3 13.2813.38 B₂O₃ 1.61 1.54 1.63 1.68 1.59 1.67 1.59 1.55 MgO 5.56 5.49 5.515.37 5.6 5.32 5.29 5.27 CaO 4.95 5.15 5.04 5.01 4.95 5.12 5.22 5.07 SrO1.03 1.12 0.97 1.06 1.03 1.06 1 1.08 BaO 3.58 3.57 3.68 3.61 3.58 3.613.68 3.59 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.09 0.09 0.09 0.08 0.08 0.090.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.010.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.13 1.15 1.14 1.13 1.14 1.14 1.141.12 Annealing point 801.4 801.0 799.0 813.0 800.2 800.0 800.3 801.7Young's modulus 83.8 84.3 84.3 83.8 84.0 82.9 83.7 84.5 Etch index 24.825.2 25.0 24.8 24.7 24.9 25.1 24.7 Density 2.602 2.605 2.604 2.603 2.6032.603 2.603 2.603 T (200P) 1658 1656 1661 1665 1655 1670 1665 1672 T(35kP) 1285 1286 1287 1289 1286 1291 1293 1291 T (liquidus) 1235 12351240 1220 1235 1230 1235 1230 Liquidus Viscosity 99725 101205 91240154337 100790 124064 117558 122727 Sample 105 106 107 108 109 110 111112 SiO₂ 69.98 69.96 70.2 70.35 70.41 70.2 70.42 70.11 Al₂O₃ 13.38 13.4113.37 13.32 13.3 13.24 13.17 13.39 B₂O₃ 1.64 1.72 1.67 1.62 1.55 1.671.71 1.8 MgO 5.1 4.97 4.93 4.35 4.38 4.64 4.47 4.55 CaO 5.01 4.97 4.935.43 5.47 5.38 5.33 5.07 SrO 1.32 1.41 1.41 1.25 1.11 1.11 0.92 1.06 BaO3.46 3.41 3.37 3.58 3.67 3.66 3.86 3.91 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.080.13 0.08 0.07 0.08 0.09 0.09 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.010.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.111.10 1.09 1.10 1.10 1.12 1.11 1.09 Annealing point 800.9 801.4 801.7805.3 804.9 801.1 801.1 801.4 Young's modulus 83.6 83.2 83.6 82.9 84.883.2 82.7 82.9 Etch index 24.7 24.6 24.1 24.6 24.5 24.7 24.2 25.0Density 2.599 2.597 2.596 2.601 2.598 2.599 2.6 2.604 T (200P) 1666 16671686 1673 1678 1680 1678 1667 T (35kP) 1292 1296 1295 1298 1297 12991302 1299 T (liquidus) 1240 1235 1235 1220 1210 1210 1210 1205 LiquidusViscosity 102206 125777 117377 178550 218096 232664 227454 266595 Sample113 114 115 116 117 118 119 120 SiO₂ 70.08 70.05 70.03 70.21 70.62 69.0568.95 69.24 Al₂O₃ 13.42 13.43 13.4 13.46 13.19 13.9 13.98 14.01 B₂O₃1.74 1.65 1.65 1.78 1.55 1.74 1.8 1.75 MgO 4.06 4.06 4.1 4.15 3.62 5.645.68 4.99 CaO 5.73 5.86 5.84 5.31 5.8 4.8 4.74 5.21 SrO 1.33 1.42 1.451.23 1.61 1.27 1.33 1.09 BaO 3.52 3.43 3.44 3.77 3.49 3.48 3.4 3.59 ZnO0 0 0 0 0 0 0 0 SnO₂ 0.08 0.07 0.07 0.08 0.08 0.1 0.1 0.09 Fe₂O₃ 0.010.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.02 0.02 0.01 0.01 0.02 0.010.01 0.02 RO/Al₂O₃ 1.09 1.10 1.11 1.07 1.10 1.09 1.08 1.06 Annealingpoint 800.6 802.6 801.8 801.6 807.8 801.7 801.1 804.0 Young's modulus83.5 83.1 83.2 83.0 82.7 84.4 84.7 83.7 Etch index 25.5 25.7 25.8 25.224.9 26.4 26.4 26.5 Density 2.601 2.6 2.602 2.602 2.602 2.605 2.6052.605 T (200P) 1669 1666 1671 1675 1687 1646 1666 1665 T (35kP) 12921290 1293 1299 1311 1281 1281 1285 T (liquidus) 1200 1210 1210 1200 12101260 1265 1250 Liquidus Viscosity 253804 192535 205963 295023 30191553250 48335 70816 Sample 121 122 123 124 125 126 127 128 SiO₂ 70.2670.39 69.85 69.91 69.99 69.41 69.61 69.58 Al₂O₃ 13.44 13.36 13.56 13.8313.75 13.93 13.85 13.67 B₂O₃ 1.76 1.77 1.88 1.5 1.54 1.77 1.77 1.94 MgO4.1 4.11 5.49 4.75 5.05 5.65 4.91 5.61 CaO 5.29 5.26 4.12 5.09 4.59 4.55.12 4.26 SrO 1.23 1.22 1.22 1.37 1.62 0.86 1.31 1.17 BaO 3.83 3.79 3.783.44 3.35 3.76 3.33 3.66 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.09 0.080.08 0.09 0.09 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.08 1.08 1.08 1.061.06 1.06 1.06 1.08 Annealing point 803.0 803.8 800.4 807.2 806.3 801.5802.4 799.1 Young's modulus 82.9 82.9 83.8 83.5 84.1 84.1 84.0 83.6 Etchindex 25.2 24.7 24.4 25.3 24.8 25.2 25.4 24.7 Density 2.597 2.602 2.6062.602 2.599 2.603 2.597 2.602 T (200P) 1679 1681 1659 1673 1670 16621667 1651 T (35kP) 1299 1300 1287 1294 1293 1285 1290 1286 T (liquidus)1200 1200 1255 1250 1260 1270 1250 1250 Liquidus Viscosity 293138 29974766447 85885 67578 47292 78823 73461 Sample 129 130 131 132 133 134 135136 SiO₂ 70.92 71.09 70.66 70.63 70.02 70 70.95 70.87 Al₂O₃ 13.28 13.1913.17 13.18 13.31 13.39 13.08 13.17 B₂O₃ 1.74 1.79 1.96 1.97 1.66 1.671.6 1.79 MgO 3.71 3.72 3.77 3.77 4.92 4.89 3.57 3.76 CaO 5.2 4.88 5.25.25 4.91 5.2 5.34 5.01 SrO 1.18 1.4 1.23 1.2 1.22 1.19 1.67 1.46 BaO3.87 3.83 3.9 3.9 3.84 3.56 3.71 3.86 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.07 0.070.07 0.07 0.08 0.08 0.07 0.06 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.010.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.05 1.051.07 1.07 1.12 1.11 1.09 1.07 Annealing point 804.3 805.8 804.5 803.8802.0 801.4 806.0 803.2 Young's modulus 82.5 82.0 82.1 82.0 83.6 83.483.6 82.1 Etch index 23.7 23.3 24.2 24.3 25.1 24.9 24.4 24.1 Density2.597 2.6 2.598 2.599 2.607 2.597 2.605 2.602 T (200P) 1688 1687 16851683 1669 1668 1693 1689 T (35kP) 1309 1310 1306 1306 1294 1293 13111309 T (liquidus) 1200 1200 1205 1200 1230 1230 1250 1230 LiquidusViscosity 366072 367712 299762 340083 133668 131035 119851 180252 Sample137 138 139 140 141 142 143 144 SiO₂ 71 70.14 70.29 70.67 70.46 71.06 7170.42 Al₂O₃ 13.13 13.35 13.2 13 13.09 13.09 13.08 13.19 B₂O₃ 1.81 1.631.63 1.56 1.62 1.46 1.63 1.74 MgO 3.79 4.7 4.47 4.41 5.16 3.89 3.63 4.44CaO 4.9 5.36 5.37 5.48 4.94 5.64 5.76 5.24 SrO 1.42 1.2 1.26 1.08 1.041.19 1.22 1.09 BaO 3.87 3.53 3.67 3.7 3.58 3.58 3.57 3.78 ZnO 0 0 0 0 00 0 0 SnO₂ 0.06 0.08 0.08 0.08 0.08 0.07 0.07 0.08 Fe₂O₃ 0.01 0.01 0.010.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01RO/Al₂O₃ 1.06 1.11 1.12 1.13 1.12 1.09 1.08 1.10 Annealing point 804.1801.7 804.8 800.3 801.1 806.8 808.0 804.2 Young's modulus 82.4 83.7 83.583.4 83.6 83.0 82.0 83.1 Etch index 23.6 24.8 24.8 23.9 23.3 23.4 23.624.3 Density 2.601 2.598 2.603 2.597 2.593 2.593 2.592 2.601 T (200P)1688 1676 1672 1681 1673 1673 1688 1673 T (35kP) 1307 1293 1298 13001303 1300 1305 1296 T (liquidus) 1220 1200 1215 1200 1225 1220 1220 1210Liquidus Viscosity 218578 256994 203181 298265 180021 191362 208334222007 Sample 145 146 147 148 149 150 151 152 SiO₂ 70.16 70.06 70.0570.08 70.45 70.14 70.24 70.67 Al₂O₃ 13.36 13.48 13.44 13.43 13.3 13.3813.29 13.07 B₂O₃ 1.77 1.73 1.74 1.76 1.66 1.68 1.68 1.57 MgO 4.46 4.434.36 4.22 4.23 4.4 4.32 4.25 CaO 5.22 5.3 5.37 5.53 5.52 5.53 5.57 5.36SrO 1.1 1.21 1.18 1.22 1.22 1.23 1.19 1.32 BaO 3.82 3.68 3.74 3.65 3.523.54 3.61 3.66 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.08 0.08 0.08 0.08 0.07 0.070.07 0.07 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.010.01 0.01 0.02 0.02 0.02 0.01 RO/Al₂O₃ 1.09 1.08 1.09 1.09 1.09 1.101.11 1.12 Annealing point 804.0 803.7 802.9 804.6 805.2 804.1 804.3806.3 Young's modulus 83.1 82.7 83.8 82.3 83.2 83.6 83.6 82.9 Etch index24.9 25.2 25.3 25.3 24.3 25.0 24.9 24.1 Density 2.604 2.604 2.603 2.6012.598 2.597 2.599 2.601 T (200P) 1675 1672 1672 1670 1673 1673 1679 1678T (35kP) 1303 1299 1297 1298 1299 1297 1304 1302 T (liquidus) 1210 12101210 1215 1220 1225 1210 1215 Liquidus Viscosity 250642 234066 226948201805 185345 159888 262331 219739 Sample 153 154 155 156 157 158 159160 SiO₂ 70.67 70.63 70.4 70.43 70.38 70.24 70.6 70.64 Al₂O₃ 13.3 13.2413.31 13.46 13.09 13.16 13.16 13.4 B₂O₃ 1.91 1.75 1.75 1.85 1.95 1.941.69 1.65 MgO 3.8 3.8 4.12 3.76 3.75 3.76 4.11 3.83 CaO 4.92 5.15 4.885.29 5.19 5.22 5.29 5.28 SrO 1.17 1.35 1.22 1.2 1.18 1.2 1.21 1.22 BaO4.09 3.97 4.21 3.91 3.88 3.9 3.83 3.88 ZnO 0 0 0 0 0.49 0.49 0 0 SnO₂0.09 0.09 0.09 0.07 0.07 0.07 0.07 0.07 Fe₂O₃ 0.01 0.01 0.01 0.01 0.010.01 0.01 0.01 ZrO₂ 0.02 0.02 0.02 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃1.05 1.08 1.08 1.05 1.07 1.07 1.10 1.06 Annealing point 804.8 806.1804.5 804.7 796.1 797.0 804.6 805.6 Young's modulus 82.0 82.5 82.6 82.082.3 82.8 82.5 82.3 Etch index 24.2 24.7 25.2 24.9 24.2 24.6 24.3 24.6Density 2.606 2.608 2.613 2.599 2.609 2.611 2.597 2.599 T (200P) 16831681 1682 1671 1679 1675 1684 1680 T (35kP) 1313 1307 1305 1302 12991299 1307 1304 T (liquidus) 1220 1200 1220 1210 1215 1215 1215 1210Liquidus Viscosity 255607 349191 209625 249804 204351 204311 244630258866 Sample 161 162 163 164 165 166 167 168 SiO₂ 70.64 70.6 70.58 70.370.52 70.78 69.81 70.39 Al₂O₃ 13.29 13.17 13.11 13.42 13.29 13.17 13.5613.43 B₂O₃ 1.72 1.68 1.68 1.91 1.87 1.76 1.81 1.84 MgO 4.12 3.9 4.064.07 3.88 3.72 2.67 4.09 CaO 5.2 5.63 5.26 5.06 4.85 4.92 6.86 5 SrO1.19 1.03 1.24 1.17 1.23 1.36 2.34 1.11 BaO 3.74 3.88 3.96 3.96 4.244.18 2.86 4.02 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.07 0.08 0.08 0.08 0.09 0.090.07 0.09 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.010.02 0.02 0.02 0.01 0.01 0.02 RO/Al₂O₃ 1.07 1.10 1.11 1.06 1.07 1.081.09 1.06 Annealing point 806.9 804.5 805.3 803.6 803.9 805.0 804.7803.9 Young's modulus 81.5 82.3 82.6 82.3 82.3 82.5 83.2 82.7 Etch index24.0 24.5 24.7 24.9 24.9 24.6 27.8 24.7 Density 2.595 2.6 2.603 2.6062.609 2.612 2.604 2.605 T (200P) 1686 1689 1674 1686 1686 1694 1677 1685T (35kP) 1308 1305 1303 1301 1308 1309 1295 1302 T (liquidus) 1230 12201230 1225 1220 1210 1270 1200 Liquidus Viscosity 175734 205013 160621167882 223645 285128 57440 311772 Sample 169 170 171 172 173 174 175 176SiO₂ 70.71 69.41 70.67 70.76 69.86 70.38 69.99 70.26 Al₂O₃ 13.35 13.6713.2 13.19 13.61 13.36 13.52 13.45 B₂O₃ 1.84 1.79 1.8 1.83 1.88 1.741.83 1.82 MgO 3.64 2.79 3.68 3.83 4.17 4.13 4.2 4.18 CaO 4.89 7.01 4.894.65 5.29 5.27 5.3 5.21 SrO 1.22 2.43 1.39 1.39 1.22 1.22 1.21 1.19 BaO4.22 2.81 4.25 4.24 3.86 3.8 3.84 3.78 ZnO 0 0 0 0 0 0 0 0 SnO₂ 0.1 0.060.09 0.09 0.08 0.08 0.08 0.08 Fe₂O₃ 0.01 0.01 0.01 0.01 0.01 0.01 0.010.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.05 1.101.08 1.07 1.07 1.08 1.08 1.07 Annealing point 807.1 802.6 805.2 804.4804.2 804.0 802.8 802.8 Young's modulus 81.7 82.8 81.8 81.8 83.2 82.982.9 82.7 Etch index 24.6 28.8 25.0 24.5 26.0 24.8 25.7 24.8 Density2.609 2.606 2.611 2.612 2.619 2.603 2.603 2.601 T (200P) 1680 1660 16971694 1656 1681 1671 1674 T (35kP) 1307 1288 1310 1309 1292 1300 12991299 T (liquidus) 1200 1280 1230 1215 >1290 1190 1260 1225 LiquidusViscosity 351625 40932 182596 251502 381805 76623 165703 Sample 177 178179 180 181 182 183 184 SiO₂ 70.19 70.19 70.19 70.21 70.22 70.75 70.8870.74 Al₂O₃ 13.46 13.46 13.46 13.45 13.44 13.37 13.31 13.3 B₂O₃ 1.781.78 1.79 1.93 1.99 1.8 1.78 1.78 MgO 3.66 3.41 3.15 4.16 4.14 3.56 3.563.7 CaO 5.31 5.32 5.31 5.06 5.04 4.88 4.89 4.98 SrO 1.23 1.23 1.23 1.131.11 1.24 1.24 1.23 BaO 3.77 3.77 3.77 3.96 3.95 4.26 4.22 4.14 ZnO 0.50.75 1 0 0 0 0 0 SnO₂ 0.08 0.08 0.08 0.08 0.08 0.1 0.1 0.1 Fe₂O₃ 0.010.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 0.020.02 0.02 RO/Al₂O₃ 1.04 1.02 1.00 1.06 1.06 1.04 1.05 1.06 Annealingpoint 801.6 800.3 797.9 802.0 803.5 805.6 807.0 805.0 Young's modulus83.5 83.2 82.8 82.5 82.9 82.2 82.2 82.3 Etch index 24.8 24.7 24.5 25.024.9 24.6 24.3 24.5 Density 2.609 2.611 2.616 2.603 2.603 2.612 2.6022.609 T (200P) 1682 1678 1670 1678 1679 1699 1700 1696 T (35kP) 12991298 1290 1304 1303 1309 1310 1308 T (liquidus) 1240 1240 1200 1200 1195Liquidus Viscosity 132042 128110 360038 366709 392214 Sample 185 186 187188 189 SiO₂ 69.78 70.37 69.65 69.57 71.06 Al₂O₃ 13.36 13.11 13.91 13.9413.07 B₂O₃ 1.71 1.98 1.73 1.81 1.47 MgO 5.44 3.72 2.87 2.43 3.65 CaO4.91 5.2 5.7 6.35 5.22 SrO 1.06 1.18 2.75 2.63 1.16 BaO 3.63 3.86 3.293.16 3.8 ZnO 0 0.49 0 0 0.48 SnO₂ 0.09 0.07 0.07 0.07 0.07 Fe₂O₃ 0.010.01 0.01 0.01 0.01 ZrO₂ 0.01 0.01 0.01 0.01 0.01 RO/Al₂O₃ 1.13 1.061.05 1.05 1.06 Annealing point 798.9 799.1 808.6 808.3 803.4 Young'smodulus 83.6 82.3 82.8 82.9 82.9 Etch index 24.8 24.2 28.7 29.1 23.0Density 2.603 2.61 2.623 2.617 2.613 T (200P) 1674 1672 1672 1676 1686 T(35kP) 1289 1296 1300 1296 1304 T (liquidus) 1230 1205 1240 1245 1220Liquidus 116376 238010 121655 99336 204831 Viscosity

TABLE 2 Sample 190 191 192 193 194 195 196 197 SiO2 71.84 71.24 70.772.05 72.04 71.86 70.83 71.14 Al2O3 12.18 12.39 12.69 12.61 12.73 12.0913.08 13.32 B2O3 1.05 2.12 2.12 1.42 1.39 1.05 1.59 0.95 MgO 4.39 4.063.88 3.84 3.65 4.42 4.09 3.63 CaO 5.26 5.17 5.13 5.33 5.28 5.26 6.577.23 SrO 1.17 1.24 1.29 1.75 1.59 1.16 0.93 1.08 BaO 3.99 3.63 3.99 2.93.21 4.03 2.81 2.53 ZnO 0 0 0 0 0 0 0 0 SnO2 0.1 0.12 0.11 0.08 0.08 0.10.07 0.08 Fe2O3 0.01 0.01 0.08 0.01 0.01 0.01 0.01 0.01 ZrO2 0.01 0.020.02 0.01 0.01 0.01 0.02 0.02 RO/Al2O3 1.215928 1.138015 1.1260841.095956 1.078555 1.229942 1.100917 1.086336 Annealing 805.4355 795 793809.1221 811.7 804.6045 803.3 818 point Young's 82.63852 81.3 82.282.62262 82.3 82.56992 82.3 84.28304 modulus Etch index 21.9840321.80912 23.78082 20.40033 20.84532 21.94227 22.56788 22.8704 Density2.587 2.604 2.581 2.57 2.573 T (200P) 1706 1681 1674 1710 1705 1707 16291635 T (35kP) 1312 1305 1305 1316 1321 1312 1280 1284 T 1200 1175 11801220 1220 1200 1180 >1260 (liquidus) Liquidus 376241.5 606709 529676.2254710.6 295398.1 373256.9 500709.9 Viscosity Sample 198 199 200 201 202203 204 205 SiO2 71.58 71.31 71.33 71.62 71.63 71.56 71.29 71.2 Al2O312.34 12.62 11.49 11.3 11.45 11.7 12.52 11.96 B2O3 1.2 2.65 1.29 0 01.27 2.42 1.82 MgO 4.34 3.54 5.21 5.42 5.98 4.86 3.91 4.52 CaO 5.26 5.135.33 5.79 5.42 5.26 5 5.71 SrO 1.18 1.17 1.28 1.54 1.4 1.4 1.2 1.76 BaO3.96 3.47 3.91 4.14 3.93 3.8 3.51 2.88 ZnO 0 0 0 0 0 0 0 0 SnO2 0.090.09 0.11 0.14 0.14 0.13 0.12 0.11 Fe2O3 0.01 0.01 0.02 0.02 0.02 0.020.01 0.02 ZrO2 0.02 0.02 0.02 0.02 0.02 0 0.02 0.02 RO/Al2O3 1.1944891.054675 1.369017 1.49469 1.461135 1.309402 1.087859 1.243311 Annealing807 796.8 793.2 803.5 804.7 791.5 793.3 794.2 point Young's 82.6139 80.282.8 83.2 83.4 82.6 81.3 83.2 modulus Etch index 22.40229 21.0806122.37395 23.8956 22.798 22.00998 21.09513 21.65186 Density 2.6 2.5682.612 2.641 2.633 2.614 2.578 2.58 T (200P) 1702 1688 1680 1688 16891685 1683 1677 T (35kP) 1310 1312 1295 1303 1303 1295 1308 1300 T 12101190 1190 1200 1200 1190 1180 1200 (liquidus) Liquidus 283765.7 490718.9331896.6 318618.2 322560.5 323644.3 576117.8 290070.4 Viscosity Sample206 207 208 209 210 211 212 213 SiO2 71.59 71.5 71.49 71.05 71.69 72.171.38 71.8 Al2O3 11.74 11.94 12.3 11.79 11.76 11.58 12.24 12.42 B2O31.99 1.35 1.67 0.83 0.81 0.79 1.75 1.64 MgO 4.17 4.49 4.03 4.93 4.734.64 4.18 4.01 CaO 5.29 5.34 5.3 5.74 5.53 5.46 5.33 5.16 SrO 2.56 1.481.26 1.43 1.39 1.37 1.26 1.22 BaO 2.53 3.76 3.81 4.07 3.92 3.88 3.72 3.6ZnO 0 0 0 0 0 0 0 0 SnO2 0.11 0.11 0.11 0.13 0.13 0.13 0.11 0.11 Fe2O30.01 0.02 0.02 0.02 0.01 0.01 0.01 0.01 ZrO2 0.01 0.01 0.01 0.02 0.020.02 0.01 0.01 RO/Al2O3 1.239353 1.262144 1.170732 1.371501 1.323981.325561 1.183824 1.126409 Annealing 793.1 799.8 798.3 796 800.1 801.1794.4 798.4 point Young's 81.8 82.2 81.9 83.1 83 81.8 82.2 82.09687modulus Etch index 20.94944 22.40757 22.14761 24.45907 22.58831 21.4957322.09737 20.93307 Density 2.574 2.603 2.597 2.632 2.62 2.613 2.595 2.591T (200P) 1686 1693 1689 1679 1696 1703 1685 1695 T (35kP) 1298 1304 13031295 1309 1312 1298 1304 T 1200 1190 1185 1180 1190 1195 1190 1190(liquidus) Liquidus 273184.9 404439.6 450027.9 431437.8 447459.2417832.3 348549.8 404582.5 Viscosity Sample 214 215 216 217 218 219 220221 SiO2 71.23 71.46 71.12 70.76 70.72 71.01 71.26 71.37 Al2O3 12.4112.59 11.2 12.25 12.14 12.36 11.86 11.84 B2O3 2.54 2.58 0.69 3 2.13 1.851.81 1.84 MgO 3.62 3.54 5.84 3.69 4.86 4.13 4.57 4.36 CaO 5.23 5.1 5.525.69 5.81 5.32 6.13 6.29 SrO 1.42 1.18 1.04 2.58 1.91 1.3 1.42 1.22 BaO3.43 3.43 4.41 1.91 2.32 3.87 2.84 2.97 ZnO 0 0 0 0 0 0 0 0 SnO2 0.10.09 0.11 0.09 0.08 0.12 0.09 0.08 Fe2O3 0.01 0.01 0.05 0.02 0.02 0.030.01 0.01 ZrO2 0.01 0.02 0.02 0.02 0.01 0.02 0.02 0.02 RO/Al2O3 1.1039481.052423 1.500893 1.132245 1.227348 1.182848 1.261383 1.253378 Annealing798.2 796.1127 792.8 785.5 786 794.4 793.4782 791.4 point Young's 8181.05578 83.1 81.1 82.65483 82 82.434 81.8 modulus Etch index 21.6255820.69529 23.76489 21.38514 21.68129 23.17525 21.31421 21.19108 Density2.57 2.633 2.551 2.559 2.602 2.572 T (200P) 1687 1705 1672 1677 16811686 T (35kP) 1310 1309 1289 1304 1295 1302 T (liquidus) 1195 1185 11851180 1180 1205 1210 Liquidus 412527.4 491868.8 328005.3 377073.8536073.1 230732.6 234784.7 Viscosity Sample 222 223 224 225 226 227 228229 SiO2 70.31 71.14 70.31 70.72 70.93 70.84 70.61 71.43 Al2O3 13.2111.82 12.42 12.9 12.03 12.19 13.13 12.4 B2O3 2.53 1.63 2.36 2.24 2.2 2.22.73 2.16 MgO 3.46 5.06 4.33 3.69 4.6 4.34 3.38 3.89 CaO 4.8 5.87 5.274.98 5.19 5.26 4.65 5.26 SrO 1.27 1.7 1.28 1.24 1.15 1.26 1.25 1.77 BaO4.15 2.66 3.88 4.09 3.76 3.78 4.12 2.97 ZnO 0 0 0 0 0 0 0 0 SnO2 0.110.1 0.11 0.1 0.11 0.11 0.1 0.09 Fe2O3 0.14 0.01 0.01 0.01 0.01 0.01 0.010.01 ZrO2 0.02 0.01 0.02 0.02 0.02 0.02 0.02 0.01 RO/Al2O3 1.0355791.29357 1.188406 1.085271 1.221945 1.200984 1.020564 1.120161 Annealing788.8 794.1 789.8 797.3 787.1 790.2 792.7 797.5 point Young's 81.582.8977 81.1 80.3 81.5 81.7 80.9 81 modulus Etch index 24.4386 21.3960224.17951 23.88871 22.27046 22.895 23.70371 21.09214 Density 2.607 2.5962.601 2.589 2.594 2.598 2.573 T (200P) 1665 1676 1670 1682 1677 16791673 1677 T (35kP) 1305 1292 1294 1305 1295 1295 1303 1306 T 1190 11801170 1170 1175 1205 1195 (liquidus) Liquidus 426531.6 416885.2 694785.4525798.2 472442.8 278595.7 387294.1 Viscosity Sample 230 231 232 233 234235 236 237 SiO2 70.21 70.4 70.74 70.92 70.74 71.51 72.23 71.33 Al2O313.27 13.25 13 12.31 12.25 12.39 12.76 11.65 B2O3 2.57 2.52 2.48 2.212.3 1.96 1.15 1.78 MgO 3.51 3.41 3.35 3.93 4.26 3.88 3.57 4.3 CaO 4.824.58 4.58 5.2 4.93 5.2 5.3 5.39 SrO 1.24 1.42 1.43 1.24 1.26 1.21 1.541.38 BaO 4.24 4.29 4.28 4.04 4.12 3.72 3.33 4.03 ZnO 0 0 0 0 0 0 0 0SnO2 0.1 0.1 0.1 0.11 0.11 0.1 0.08 0.1 Fe2O3 0.01 0.01 0.01 0.01 0.010.01 0.01 0.01 ZrO2 0.02 0.02 0.02 0.02 0.02 0.01 0.01 0.02 RO/Al2O31.040693 1.033962 1.049231 1.170593 1.189388 1.130751 1.076803 1.296137Annealing 794.7 796.5 795.9 792.5 791.7 795.5 813.7858 789.5 pointYoung's 81.6 81.1 80.7 80.7 81.1 81.3 82.6638 81.7 modulus Etch index25.05352 24.90785 24.11577 23.27226 23.43973 21.61804 20.8276 22.79115Density 2.606 2.606 2.605 2.602 2.605 2.585 2.606 T (200P) 1673 16721681 1684 1687 1689 1719 1689 T (35kP) 1297 1304 1307 1302 1302 13081322 1300 T 1210 1215 1190 1190 1205 1180 1220 1175 (liquidus) Liquidus219801 231632 431798.8 377500.1 266069.2 551290.9 290830.5 508628.1Viscosity Sample 238 239 240 241 242 243 244 245 SiO2 71.02 70.54 71.3471.27 71.32 71.27 72.29 71.13 Al2O3 12.62 13.29 11.63 11.65 11.59 11.5212.76 11.27 B2O3 2 2.72 1.78 1.8 1.88 1.95 1.1 0.91 MgO 4.24 3.49 4.194.29 4.09 4.29 3.59 5.68 CaO 5.11 4.55 5.53 5.46 5.7 5.5 5.3 5.46 SrO1.17 1.1 1.28 1.21 1.07 0.89 1.53 1.1 BaO 3.69 4.18 4.12 4.18 4.21 4.433.32 4.27 ZnO 0 0 0 0 0 0 0 0 SnO2 0.11 0.1 0.1 0.1 0.1 0.1 0.08 0.11Fe2O3 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.04 ZrO2 0.02 0.02 0.02 0.020.02 0.02 0.01 0.02 RO/Al2O3 1.12599 1.002257 1.300086 1.299571 1.3002591.311632 1.076803 1.464951 Annealing 797.3 795.7 788.5 789.1 789.1 787.5816.3 791.7 point Young's 82.4 80.9 81.2 81.4 81.3 81.3 83.1 82.4modulus Etch index 22.36433 23.68105 22.9597 22.99637 22.90863 22.829820.72019 23.39862 Density 2.59 2.596 2.606 2.607 2.607 2.611 2.587 2.629T (200P) 1685 1679 1686 1688 1690 1689 1697 1675 T (35kP) 1305 1306 13021302 1299 1299 1324 1290 T 1180 1220 1180 1180 1180 1190 1220 1190(liquidus) Liquidus 536290.9 212391.7 477341 469814.6 444046.2 343194.4326959.3 293380 Viscosity Sample 246 247 248 249 250 251 252 253 SiO270.99 71.54 71.22 71.48 71.19 71.48 71.59 71.49 Al2O3 11.8 12.52 11.6711.36 11.59 11.58 11.55 11.57 B2O3 1.2 2.29 1.7 1.45 1.55 1.52 1.53 1.61MgO 5.57 3.64 4.85 4.87 5.02 4.53 4.33 4.4 CaO 5.36 5.07 5.31 5.35 5.445.43 5.52 5.45 SrO 1.84 1.19 1.15 0.98 1.21 1.37 1.29 1.22 BaO 3.08 3.643.97 4.38 3.86 3.96 4.04 4.12 ZnO 0 0 0 0 0 0 0 0 SnO2 0.11 0.1 0.1 0.10.1 0.1 0.1 0.1 Fe2O3 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO2 0.030.01 0.02 0.02 0.02 0.02 0.02 0.02 RO/Al2O3 1.34322 1.08147 1.309341.371479 1.339948 1.32038 1.314286 1.312878 Annealing 795.7 797.5 790.9789.7 791.6 792.7 793.2 794.7 point Young's 83.1 81.3 81.9 82 83 82.281.8 80.9 modulus Etch index 22.44066 21.13801 22.40309 22.5177322.47967 22.49214 22.3657 22.50857 Density 2.6 2.578 2.602 2.617 2.6052.608 2.609 2.61 T (200P) 1675 1698 1686 1686 1680 1688 1694 1699 T(35kP) 1292 1311 1298 1300 1295 1304 1302 1304 T 1195 1175 1175 12001190 1185 1180 1180 (liquidus) 277980.5 668710.1 494723.9 285342.4324060.7 440344.3 474815.8 494159.7 Liquidus Viscosity Sample 254 255256 257 258 259 260 261 SiO2 71.51 71.48 72.45 72.99 72.36 72.04 72.4772.95 Al2O3 11.58 11.77 12.55 12.52 12.92 12.67 12.35 12.14 B2O3 1.621.55 1.39 0.88 0.74 1.01 1.15 1.17 MgO 4.23 4.46 3.51 3.58 3.7 4.02 4.084 CaO 5.65 5.52 5.21 5.12 5.22 5.11 4.97 4.87 SrO 1.08 1.14 1.51 1.291.24 1.24 1.2 1.18 BaO 4.2 3.96 3.26 3.51 3.7 3.79 3.66 3.57 ZnO 0 0 0 00 0 0 0 SnO2 0.1 0.09 0.09 0.08 0.08 0.09 0.09 0.09 Fe2O3 0.01 0.01 0.010.01 0.01 0.01 0.01 0.01 ZrO2 0.02 0.01 0.01 0.02 0.02 0.02 0.02 0.02RO/Al2O3 1.309154 1.281223 1.0749 1.078275 1.072755 1.117601 1.1263161.121911 Annealing 794.6 795.5 813.2 822 821.3 813 811.7 811.3 pointYoung's 81.6 81.9 82.2 83.1 83.6 83.3 83 82.3 modulus Etch index22.64522 22.29207 19.83529 19.16165 21.09868 21.45792 19.84445 18.45087Density 2.61 2.608 2.579 2.584 2.598 2.597 2.59 2.581 T (200P) 1695 16821699 1729 1713 1705 1712 1720 T (35kP) 1303 1300 1321 1337 1334 13261324 1332 T 1175 1170 1200 1230 1210 1210 1205 1230 (liquidus) Liquidus548444.6 608512.8 479431.2 323282.9 507430.5 412573.2 434357.2 291555.9Viscosity Sample 262 263 264 265 266 267 268 269 SiO2 72.36 72.2 72.1371.8 71.87 71.45 71.51 71.36 Al2O3 12.34 12.49 12.44 12.38 12.07 12.4912.24 12.58 B2O3 1.01 0.95 0.85 1.58 1.05 2.51 1.62 2.45 MgO 4.37 4.54.71 4.28 4.46 3.54 4.65 3.86 CaO 5.36 5.58 5.67 5.52 5.25 5.28 5.664.94 SrO 2.62 3.16 3.2 2.73 1.16 1.16 2.59 1.19 BaO 1.82 1.01 0.88 1.594.03 3.45 1.61 3.47 ZnO 0 0 0 0 0 0 0 0 SnO2 0.09 0.09 0.09 0.09 0.10.09 0.09 0.12 Fe2O3 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO2 0.020.01 0.01 0.01 0.02 0.02 0.01 0.02 RO/Al2O3 1.148298 1.140913 1.1623791.140549 1.234466 1.07526 1.185458 1.069952 Annealing 812.6031 810.9813.4 802.6 804.3335 797.4 798.6 796.4516 point Young's 83.50687 84.884.6 82.3 82.57827 81.8 83.6 81.33516 modulus Etch index 19.0315318.89465 18.90793 19.65592 21.93579 20.90369 20.02251 20.80924 Density2.548 2.547 2.553 2.571 2.556 0 T (200P) 1706 1691 1691 1685 1706 16891676 1702 T (35kP) 1314 1313 1310 1307 1312 1309 1301 1308 T 1240 12601265 1240 1205 1190 1250 1195 (liquidus) Liquidus 159186.9 101972.685719.78 137559.8 328769.2 453473.6 97743.74 377911.9 Viscosity Sample270 271 272 273 274 275 276 277 SiO2 71.39 72.63 72.86 71.58 71.85 69.9270.66 71.97 Al2O3 12.45 12.35 11.08 12.39 12.63 12.46 12.29 12.33 B2O32.28 1.04 0.28 2.39 1.69 1.66 1.81 1.24 MgO 3.93 4.48 7.28 3.52 3.915.78 4.87 4.32 CaO 5.18 4.78 3.91 5.35 5.05 6.42 6.04 5.23 SrO 1.59 1.060.45 1.16 1.2 1.64 1.52 1.2 BaO 3.06 3.54 4.04 3.48 3.53 2.02 2.67 3.59ZnO 0 0 0 0 0 0 0 0 SnO2 0.09 0.09 0.09 0.09 0.11 0.09 0.09 0.1 Fe2O30.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO2 0.01 0.02 0.01 0.02 0.01 00.02 0.01 RO/Al2O3 1.105221 1.122267 1.415162 1.090395 1.083927 1.2728731.228641 1.163017 Annealing 798.8 812.3432 809.4 798.7 806 794.4814795.0042 805.9 point Young's 82.2 82.8007 83.8 80.8 82.13926 84.3411483.05592 82.7 modulus Etch index 20.90878 18.84683 17.00156 20.7940520.6446 23.1501 22.34058 20.84849 Density 2.571 2.596 2.573 2.584 2.589T (200P) 1680 1723 1708 1690 1701 1642 1668 1704 T (35kP) 1306 1324 13211310 1314 1275 1289 1318 T 1200 1250 1275 1200 1185 1255 1190 (liquidus)Liquidus 340722.7 152460.4 87073.22 368579.7 583021.9 52829.21 554503Viscosity Sample 278 279 280 281 282 283 284 285 SiO2 70.86 71.83 71.4472.51 71.39 71.28 71.23 72.71 Al2O3 11.75 12.08 12.41 12.49 12.61 12.5712.56 11.22 B2O3 1.31 1.05 1.29 1.04 2.41 2.59 2.69 0.23 MgO 5.53 4.444.35 4.27 3.85 3.07 3.83 6.66 CaO 5.4 5.26 5.2 4.92 4.93 5.7 4.9 3.65SrO 1.77 1.16 1.15 1.18 1.18 1.17 1.18 2.49 BaO 3.22 4.04 4.03 3.47 3.493.49 3.47 2.93 ZnO 0 0 0 0 0 0 0 0 SnO2 0.11 0.1 0.09 0.09 0.11 0.1 0.110.09 Fe2O3 0.02 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO2 0.02 0.02 0.020.02 0.02 0.02 0.02 0.01 RO/Al2O3 1.354894 1.233444 1.186946 1.1080861.066614 1.068417 1.065287 1.401961 Annealing 793.1 804.3726 803.5725813.2185 800.4 795.7 795.7 812 point Young's 83.3 82.57328 82.5580882.84625 81.4 80.9 80.8 84.2 modulus Etch index 22.82465 21.995422.71064 19.3897 20.82856 21.8111 20.86149 18.3739 Density 2.601 2.6012.574 2.574 2.57 2.598 T (200P) 1673 1706 1700 1721 1685 1688 1682 1707T (35kP) 1289 1312 1309 1323 1310 1312 1305 1320 T 1190 1215 1195 12201195 1180 1180 1255 (liquidus) Liquidus 294185.9 260080.1 394781.1297066.7 423662.6 618602.3 528537.5 128091.6 Viscosity Sample 286 287288 289 290 291 292 293 SiO2 72.62 72.29 72.32 71.73 71.25 69.76 71.3371.27 Al2O3 12.37 11.9 11.74 12.36 12.59 13.31 12.54 12.54 B2O3 1.040.38 0.16 1.63 2.64 2.08 2.2 2.17 MgO 4.52 4.99 5.08 3.66 3.3 4.53 3.763.86 CaO 4.74 5.24 5.37 5.64 5.42 6.43 5.31 5.3 SrO 1.04 1.15 1.18 1.181.17 1.02 1.61 1.73 BaO 3.54 3.91 4.03 3.68 3.48 2.75 3.13 3.03 ZnO 0 00 0 0 0 0 0 SnO2 0.09 0.09 0.09 0.1 0.1 0.09 0.09 0.09 Fe2O3 0.01 0.010.01 0.01 0.01 0.01 0.01 0.01 ZrO2 0.02 0.02 0.02 0.02 0.02 0.02 0.010.01 RO/Al2O3 1.118836 1.284874 1.333901 1.145631 1.061954 1.1066871.101276 1.110048 Annealing 813.8 811.2404 814.7 799 795 794.9 798 796.5point Young's 82.83213 83.46431 83.60945 81.94595 75.9 83.4 81.7080981.8 modulus Etch index 18.77549 21.04342 21.51927 21.75296 21.4654824.26216 21.47102 21.61943 Density 2.578 2.619 2.591 2.572 2.573 2.5742.575 T (200P) 1715 1710 1707 1689 1653 1698 1691 T (35kP) 1326 13161324 1309 1284 1306 1307 T 1240 1220 1225 1175 1190 1210 1185 (liquidus)Liquidus 204010 254527.6 278235.6 640934.2 275491.3 255656.1 475116Viscosity Sample 294 295 296 297 298 299 300 301 SiO2 71.33 71.68 71.872.36 72.04 71.45 71.3 71.32 Al2O3 12.54 12.07 11.91 11.65 12.2 12.3612.41 12.45 B2O3 2.05 1.39 1.13 1.06 2.41 2.6 2.63 2.53 MgO 3.97 4.394.56 4.66 3.17 3.52 3.59 3.68 CaO 5.37 5.39 5.42 5.4 5.2 5.05 5.05 5.12SrO 1.77 1.36 1.21 1.11 2.55 1.96 1.82 1.45 BaO 2.86 3.6 3.84 3.63 2.312.93 3.09 3.34 ZnO 0 0 0 0 0 0 0 0 SnO2 0.08 0.09 0.09 0.1 0.1 0.1 0.10.1 Fe2O3 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO2 0.01 0.02 0.020.01 0.02 0.01 0.01 0.01 RO/Al2O3 1.114035 1.22121 1.261965 1.2703861.084426 1.088997 1.091861 1.091566 Annealing 798.4 800.843 801.3 800.3798 797.5 795.8 795.8 point Young's 82.2 82.39273 81.9 82.7 83.5 80.980.6 81.3 modulus Etch index 21.32183 21.6436 21.73829 19.88012 19.5927420.79872 21.23157 21.23147 Density 2.572 2.592 2.603 2.609 2.554 2.5622.565 2.57 T (200P) 1679 1700 1688 1694 1697 1691 1676 1678 T (35kP)1304 1307 1308 1313 1318 1314 1308 1307 T 1190 1200 1195 1190 1190 12001180 1190 (liquidus) Liquidus 415004.2 337331.2 402056.3 489179.1543289.1 400055 575999 442857.5 Viscosity Sample 302 303 304 305 306 307308 309 SiO2 71.2 71.31 71.15 71.29 71.54 72.09 70.45 71.17 Al2O3 12.4412.59 12.58 12.4 11.03 10.81 13.17 12.55 B2O3 2.54 2.37 2.62 2.63 0 02.47 1.92 MgO 3.71 3.7 3.52 3.54 5.47 5.34 3.53 3.94 CaO 5.19 5.24 5.385.4 5.94 5.84 4.83 5.17 SrO 1.4 1.42 1.18 1.16 1.55 1.52 1.24 1.24 BaO3.4 3.26 3.44 3.47 4.29 4.22 4.17 3.89 ZnO 0 0 0 0 0 0 0 0 SnO2 0.1 0.090.09 0.09 0.14 0.14 0.1 0.1 Fe2O3 0.01 0.01 0.01 0.01 0.02 0.02 0.010.01 ZrO2 0.01 0.02 0.02 0.02 0.02 0.02 0.02 0.02 RO/Al2O3 1.1012861.081811 1.074722 1.094355 1.563917 1.565217 1.045558 1.134661 Annealing797.1 796.6 795.6 794.3 799.8 798.7 795.6 795.4 point Young's 81.4 81.781 81.2 83.5 83.4 81.3 81.9 modulus Etch index 21.54734 21.3273621.57075 21.28039 24.42145 22.92993 24.44992 22.7997 Density 2.572 2.5722.573 2.57 2.652 2.645 2.602 2.594 T (200P) 1684 1682 1682 1689 16821684 1681 1687 T (35kP) 1309 1310 1307 1309 1296 1298 1304 1306 T 11901190 1185 1180 1190 1205 1195 1165 (liquidus) Liquidus 457698.6 471657.5491185 575435.4 344528.5 248518.1 366301.6 786689.9 Viscosity Sample 310311 312 313 314 315 316 317 SiO2 71.14 70.86 70.99 71.35 71.39 72.5172.24 71.14 Al2O3 11.82 12.07 12.03 11.78 12.65 12.31 12.51 11.79 B2O31.63 1.67 1.61 1.59 2.62 1.37 0.95 1.72 MgO 5.06 5.17 5.14 4.98 3.773.54 4.15 4.64 CaO 5.87 5.71 5.7 5.85 4.84 5.28 5.4 6.59 SrO 1.7 2.021.99 1.67 1.17 3.19 2.19 1.19 BaO 2.66 2.38 2.42 2.68 3.41 1.7 2.43 2.82ZnO 0 0 0 0 0 0 0 0 SnO2 0.1 0.1 0.09 0.09 0.12 0.08 0.1 0.08 Fe2O3 0.010.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO2 0.01 0.01 0.01 0.01 0.02 0.010.01 0.02 RO/Al2O3 1.29357 1.265949 1.267664 1.288625 1.042688 1.1137291.132694 1.292621 Annealing 794.1 795.1323 793.6 793.2 795.8 810.1711813.7264 792.8048 point Young's 82.8977 83.19961 83.2 83.1 81.5 82.5710983.37436 82.66717 modulus Etch index 21.39602 21.82925 21.6186 21.0068420.41822 19.28765 20.01173 21.59617 Density 2.574 2.575 2.57 T (200P)1676 1670 1669 1676 1690 1715 1709 1675 T (35kP) 1292 1290 1293 12971307 1318 1316 1291 T 1200 1210 1190 1230 (liquidus) Liquidus 251949214753.2 434855.9 211230.1 Viscosity Sample 318 319 320 321 322 323 324325 SiO2 70.19 71.04 68.14 70.44 71.94 70.69 70.39 70.74 Al2O3 13.0711.79 12.54 12.15 12.25 12.37 12.49 13.09 B2O3 2.26 1.69 0.92 1.51 1.011.83 1.92 1.67 MgO 4.63 4.77 7.2 5.81 4.62 4.91 4.99 5.19 CaO 6.17 6.717.07 5.81 5.45 5.81 5.18 4.04 SrO 0.02 1.17 2.71 2.11 1.24 1.62 1.181.84 BaO 3.55 2.72 1.31 2.06 3.38 2.65 3.73 3.34 ZnO 0 0 0 0 0 0 0 0SnO2 0.09 0.08 0.09 0.1 0.09 0.09 0.09 0.08 Fe2O3 0.01 0.01 0.01 0.010.01 0.01 0.01 0.01 ZrO2 0.02 0.02 0 0 0.02 0.02 0.01 0 RO/Al2O31.099464 1.303647 1.458533 1.299588 1.199184 1.211803 1.207366 1.10084Annealing 794.3 788.7 793.0213 795.3731 807.6744 792.1 794.1 805 pointYoung's 83.5 82.6 86.64271 84.02072 83.1448 83.2 82.4 82.9 modulus Etchindex 22.87987 21.66993 28.00262 22.31177 20.84279 22.23753 23.7284122.68145 Density 2.575 2.57 2.574 2.6 2.593 T (200P) 1659 1679 1592 16551702 1666 1670 1690 T (35kP) 1290 1290 1248 1282 1311 1290 1290 1304 T1210 1210 >1250 1270 1200 1200 1155 1240 (liquidus) Liquidus 192476.4181711 44402.08 371517.1 239421.5 702527.8 129265.8 Viscosity Sample 326327 328 329 330 331 332 333 SiO2 70.27 71.82 72.5 71.74 71.2 70.52 72.2271.86 Al2O3 12.84 12.29 12.21 12.97 11.59 12.43 11.77 12.07 B2O3 2.011.02 0.27 0.38 1.19 2.99 0.62 1.05 MgO 4.83 5.14 5.18 5.14 5.32 3.84 6.64.44 CaO 5.69 5.28 5.37 5.34 5.36 5.06 3.38 5.26 SrO 1.63 2.03 1.59 1.571.4 1.2 2.09 1.17 BaO 2.61 2.31 2.76 2.76 3.78 3.84 3.2 4.03 ZnO 0 0 0 00 0 0 0 SnO2 0.09 0.09 0.09 0.09 0.11 0.09 0.09 0.1 Fe2O3 0.01 0.01 0.010.01 0.02 0.01 0.01 0.01 ZrO2 0.02 0 0 0 0.02 0.02 0.01 0.01 RO/Al2O31.149533 1.200976 1.220311 1.141866 1.368421 1.12148 1.297366 1.234466Annealing 794 808.4483 817.8526 820.4832 795.1 787.8 807.6 807 pointYoung's 83.6 83.82911 84.36218 84.89179 83.3 80.3 84 82.56772 modulusEtch index 23.01219 19.9231 19.30305 21.10905 22.69538 23.03402 18.9629621.96634 Density 2.575 2.612 2.585 2.596 2.601 T (200P) 1651 1691 17061693 1680 1674 1697 1706 T (35kP) 1286 1306 1316 1311 1294 1292 13161312 T 1190 1310 1270 1260 1200 1165 1260 1200 (liquidus) Liquidus283259 32303.36 87589.07 98776.53 255014.6 550608.6 108909.5 370555.6Viscosity Sample 334 335 336 337 338 339 340 341 SiO2 70.64 71.56 70.5369.39 70.88 71.13 71.52 70.89 Al2O3 12.82 12.87 13.58 13.54 12.63 12.4711.95 12.13 B2O3 2.33 1.17 1.29 2.17 1.93 1.82 1.92 1.05 MgO 4.1 5.065.08 4.81 3.55 3.19 3.95 6.04 CaO 6.18 5.18 5.16 6.21 7.06 7.35 6.515.14 SrO 0.12 1.97 2 1.11 0.48 0.63 0.88 1.37 BaO 3.68 2.06 2.25 2.643.36 3.29 3.17 3.25 ZnO 0 0 0 0 0 0 0 0 SnO2 0.09 0.12 0.09 0.09 0.090.09 0.08 0.1 Fe2O3 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO2 0.02 00 0.02 0.02 0.02 0.02 0.01 RO/Al2O3 1.098284 1.10878 1.06701 1.0908421.144101 1.159583 1.214226 1.302556 Annealing 794.6 812.23 812.5898794.2 798.1 798 792.9 800.6779 point Young's 82.4 84.17108 84.64822 83.682.4 82.5 82.2 83.98618 modulus Etch index 22.31073 19.86527 22.671224.68895 22.9674 22.90319 21.03888 22.22297 Density 2.574 2.573 2.5752.577 2.572 T (200P) 1670 1688 1670 1644 1666 1691 1683 1672 T (35kP)1297 1306 1297 1280 1295 1308 1301 1293 T 1185 1240 1260 1220 1190 11901170 (liquidus) Liquidus 396614.3 136428.3 75061.55 124995.4 348107.7448058.3 612361.5 Viscosity Sample 342 343 344 345 346 347 348 349 SiO270.62 70.78 70.84 71.16 71.54 70.51 72.29 71.63 Al2O3 13.09 13.01 12.7613.66 12.46 12.87 12.28 12.53 B2O3 1.5 1.34 2.05 0.52 2.47 2.25 0.831.32 MgO 4.84 4.87 3.85 5.04 3.47 4.28 1.09 3.32 CaO 5.75 5.66 6.46 5.255.19 6.09 9.97 7.26 SrO 1.52 1.63 0.86 1.54 1.38 0.44 0.41 1.08 BaO 2.582.59 3.08 2.72 3.39 3.44 3.01 2.73 ZnO 0 0 0 0 0 0 0 0 SnO2 0.08 0.080.07 0.09 0.08 0.09 0.1 0.08 Fe2O3 0.01 0.01 0.01 0.01 0.01 0.01 0.010.01 ZrO2 0.02 0.02 0.02 0 0.01 0.02 0.02 0.02 RO/Al2O3 1.1222311.133743 1.116771 1.065154 1.077849 1.107226 1.179153 1.148444 Annealing802.9 804.7 795 823.3371 798.2 796.0502 818.8 808.5 point Young's 83.384.7 82.3 85.27518 81.04604 82.47254 82 82.7 modulus Etch index 22.6328422.45787 22.4536 22.28574 20.94774 22.59134 23.17745 21.72726 Density2.575 2.577 2.571 2.569 2.576 2.567 T (200P) 1661 1668 1669 1685 16901675 1704 1686 T (35kP) 1296 1300 1298 1308 1310 1294 1324 1312 T 11901190 1180 1260 1170 1210 >1300 1250 (liquidus) Liquidus 367592.1396125.9 463848.9 94542.68 757926.6 204023.8 124458.6 Viscosity Sample350 351 352 353 354 355 356 357 SiO2 71.55 72.22 70.97 72.65 72.53 71.5671.49 71.08 Al2O3 12.65 12.3 12.4 11 11.27 12.45 12.47 12.09 B2O3 1.521.7 1.98 0.08 0.19 2.41 2.42 1.1 MgO 4.51 4.46 4.01 7.31 6.94 3.54 3.575.96 CaO 5.73 5.4 6.51 3.92 4.22 5.17 5.18 4.98 SrO 1.39 1.37 0.88 1.821.49 1.38 1.38 1.51 BaO 2.54 2.44 3.15 3.12 3.24 3.4 3.4 3.17 ZnO 0 0 00 0 0 0 0 SnO2 0.08 0.08 0.08 0.09 0.09 0.08 0.08 0.09 Fe2O3 0.01 0.010.01 0.01 0.01 0.01 0.01 0.01 ZrO2 0.02 0.02 0.02 0.01 0.01 0.01 0.010.01 RO/Al2O3 1.120158 1.111382 1.173387 1.47 1.409938 1.083534 1.0850041.291977 Annealing 803.2 802.3 794.6 808.9 809.7 796.296 796.025 797.5point Young's 83.2 82.6 82.3 84.1 83.8 81.13427 81.16879 83.7 modulusEtch index 20.24181 18.02948 22.27053 17.92624 18.23479 20.9538821.10237 21.75035 Density 2.563 2.551 2.573 2.596 2.595 2.594 T (200P)1680 1697 1676 1699 1702 1706 1704 1672 T (35kP) 1310 1315 1296 13161315 1309 1308 1297 T 1230 1235 1195 >1285 1270 1220 (liquidus) Liquidus187896.9 182059.8 307135.7 84862.08 175526.4 Viscosity Sample 358 359360 361 362 363 364 365 SiO2 71.06 71.54 71.62 72.62 73.01 72.89 73.0673.16 Al2O3 12.11 11.79 11.64 10.9 10.72 10.94 10.9 10.67 B2O3 1.01 0.930.64 0.21 0.23 0.36 0.41 0.23 MgO 5.99 6.02 6.61 7.03 7.07 7.73 7.517.38 CaO 5.08 4.5 4.4 4.33 4.41 3.32 3.23 3.74 SrO 1.37 2.57 2.15 1.511.41 0.77 1.63 1.56 BaO 3.26 2.54 2.84 3.28 3.04 3.88 3.13 3.14 ZnO 0 00 0 0 0 0 0 SnO2 0.09 0.09 0.09 0.09 0.09 0.09 0.09 0.09 Fe2O3 0.01 0.010.01 0.01 0.01 0.01 0.01 0.01 ZrO2 0.01 0.01 0.01 0.01 0.01 0.01 0.010.01 RO/Al2O3 1.296449 1.3257 1.37457 1.481651 1.486007 1.4351011.422018 1.482662 Annealing 798.1 799.3 800.8 806.1 806 808 806.8 808.1point Young's 83.4 83.4 83.8 83.8 83.8 83.6 84.5 84.2 modulus Etch index21.88896 20.78711 20.49126 18.07284 16.59969 16.33879 15.73304 15.99909Density 2.594 2.592 2.596 2.596 2.582 2.592 2.583 2.582 T (200P) 16681675 1677 1698 1701 1707 1708 1711 T (35kP) 1297 1302 1300 1312 13171320 1320 1321 T 1220 1215 1225 1280 1290 >1300 1300 >1295 (liquidus)Liquidus 176802.1 217348.4 166314.4 65505.18 58957.97 50968.15 ViscositySample 366 367 368 369 370 371 372 373 SiO2 72.78 71.19 70.36 72.4672.88 72.95 72.92 73.17 Al2O3 10.93 12.44 12.52 11.5 11.07 11.11 10.910.75 B2O3 0.1 1.6 2.91 0.51 0.23 0.07 0.17 0.2 MgO 7.32 4.43 3.95 6.786.87 6.84 6.97 7.17 CaO 3.89 5.48 5.11 3.36 4.22 3.74 3.32 3.96 SrO 1.751.07 1.2 2.09 0.89 2.37 3.27 1.51 BaO 3.12 3.69 3.83 3.18 3.73 2.81 2.343.12 ZnO 0 0 0 0 0 0 0 0 SnO2 0.09 0.08 0.09 0.09 0.09 0.09 0.09 0.09Fe2O3 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO2 0.01 0.01 0.02 0.010.01 0.01 0.01 0.01 RO/Al2O3 1.47118 1.17926 1.125399 1.34 1.4191511.418542 1.458716 1.466047 Annealing 809.2 800 788.8 807.6 809.4 811.3808 807.8 point Young's 84.1 80.6 80.7 84.1 84.7 84.1 84.3 84 modulusEtch index 17.44481 22.48081 23.46576 18.33199 17.44799 17.5484917.53955 16.16689 Density 2.592 2.592 2.584 2.595 2.597 2.591 2.5932.584 T (200P) 1703 1684 1676 1703 1705 1708 1714 1710 T (35kP) 13171302 1292 1319 1321 1321 1317 1321 T >1270 1195 1170 1255 1280 12801280 >1290 (liquidus) Liquidus 345017.6 487482.8 127262.8 77703.3468543.02 65484.62 Viscosity Sample 374 375 376 377 378 379 380 381 SiO272.96 72.89 72.79 71.98 72.06 72.05 72.31 72.32 Al2O3 11.12 11.27 11.4812.16 12.23 12.53 12.25 12.43 B2O3 0.2 0.2 0.25 0.56 0.53 0.62 0.44 0.45MgO 6.36 6.09 6.23 5.62 5.94 5.12 5.02 5.1 CaO 3.9 3.87 3.91 4.56 4 4.694.68 4.66 SrO 2.7 3.1 2.14 1.74 1.76 1.6 2.29 1.51 BaO 2.64 2.46 3.083.27 3.37 3.29 2.9 3.41 ZnO 0 0 0 0 0 0 0 0 SnO2 0.09 0.09 0.09 0.090.09 0.09 0.09 0.09 Fe2O3 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO20.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al2O3 1.402878 1.3771071.337979 1.249178 1.232216 1.173184 1.21551 1.181014 Annealing 810.2811.4 811.7 809.9 811.6 811.6 814.3 817.9 point Young's 84 84 83.8 83.984 84.3 84.5 83.8 modulus Etch index 17.86931 18.40311 18.35774 20.5948820.12042 20.63091 20.43909 20.19099 Density 2.59 2.592 2.594 2.598 2.5982.597 2.596 2.597 T (200P) 1712 1715 1711 1697 1702 1706 1700 1704 T(35kP) 1323 1324 1325 1320 1318 1320 1321 1324 T 1280 1250 1260 12201230 1220 1220 1220 (liquidus) Liquidus 69511.87 156090.9 127513.5287263.6 218144.5 257540.4 263908.4 278800.4 Viscosity Sample 382 383384 385 386 387 388 389 SiO2 71.71 71.84 71.18 71.19 71.64 71.84 71.6871.08 Al2O3 12.09 12.08 12.57 12.59 12.64 12.79 12.84 12.26 B2O3 1.080.98 1.18 1.22 0.96 1 0.87 2.12 MgO 4.5 4.51 4.71 4.7 4.07 3.99 4.842.18 CaO 5.42 5.29 5.5 5.51 5.53 5.14 4.79 8.35 SrO 1.14 1.16 1.32 1.331.31 1.38 1.17 0.51 BaO 3.92 4 3.43 3.33 3.72 3.73 3.68 3.37 ZnO 0 0 0 00 0 0 0 SnO2 0.1 0.1 0.09 0.08 0.1 0.1 0.1 0.08 Fe2O3 0.01 0.01 0.010.01 0.01 0.01 0.01 0.01 ZrO2 0.02 0.02 0.02 0.02 0.02 0.02 0.02 0.02RO/Al2O3 1.239041 1.238411 1.190135 1.181096 1.157437 1.11337 1.1277261.175367 Annealing 804.1 805.4 804.6 804.9 810.9 813.8 813.1 795.5 pointYoung's 82.6 82.6 83.2 83.35358 83.07044 83.1 83.8 81.4 modulus Etchindex 22.08195 21.95745 22.68694 22.42529 22.64597 22.05351 21.5296123.8085 Density 2.605 2.611 2.596 2.594 2.606 2.601 2.601 2.577 T (200P)1693 1693 1685 1682 1699 1708 1695 1683 T (35kP) 1313 1315 1303 13021313 1321 1315 1299 T 1185 1190 1190 1190 1190 1180 1190 1230 (liquidus)Liquidus 569667.5 536744.4 397758.3 393454.2 511895.1 778849.7 539338.6142246.1 Viscosity Sample 390 391 392 393 394 395 396 397 SiO2 72.3372.68 71.29 71.24 71.99 72.05 72.26 71.14 Al2O3 12.39 12.46 13.23 13.3512.8 12.5 12.44 11.82 B2O3 0.87 0.45 1.2 1.12 0.37 0.94 0.99 1.63 MgO4.38 5.08 5.17 5.33 5.41 4.55 4.47 5.06 CaO 5.63 4.77 3.78 3.47 4.69 5.15.6 5.87 SrO 1.09 1.29 1.94 1.94 1.36 1.25 3.04 1.7 BaO 3.21 3.16 3.293.47 3.25 3.49 1.1 2.66 ZnO 0 0 0 0 0 0 0 0 SnO2 0.07 0.07 0.07 0.070.07 0.09 0.09 0.1 Fe2O3 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO20.02 0.02 0 0 0.02 0.02 0.01 0.01 RO/Al2O3 1.154964 1.147673 1.0718071.064419 1.149219 1.1512 1.142283 1.29357 Annealing 812.7514 820.2 811.1799.4 819.8 812 813.8677 794.1 point Young's 83.32084 84.1 83.6 83.584.7 83 83.99441 82.8977 modulus Etch index 19.84819 18.70819 21.7600722.05945 20.45227 20.68442 18.75206 21.39602 Density 2.582 2.595 2.6012.592 2.591 2.552 T (200P) 1710 1706 1693 1698 1703 1694 1697 1676 T(35kP) 1317 1328 1311 1312 1316 1318 1311 1292 T 1220 1240 1240 12601265 1210 1250 (liquidus) Liquidus 263835.1 218400.7 151844.1 100264.297254.47 358760.1 Viscosity Sample 398 399 400 401 402 403 404 405 SiO271.83 72.85 72.18 71.78 70.25 70.54 71.82 72.35 Al2O3 12.12 11.17 12.0512.38 12.6 12.8 12.24 12.06 B2O3 1.05 0.09 0.6 0.82 2.09 1.71 0.88 0.43MgO 4.44 6.79 5.41 4.96 4.83 4.83 4.85 5.3 CaO 5.25 3.83 4.78 5.16 5.775.72 5.57 4.8 SrO 1.17 2.34 1.69 1.47 1.5 1.6 1.26 1.74 BaO 4.02 2.833.16 3.31 2.85 2.7 3.28 3.21 ZnO 0 0 0 0 0 0 0 0 SnO2 0.1 0.09 0.1 0.10.08 0.08 0.08 0.08 Fe2O3 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 ZrO20.02 0.01 0.01 0.01 0.02 0.02 0.02 0.01 RO/Al2O3 1.227723 1.4136081.248133 1.203554 1.186508 1.160156 1.222222 1.247927 Annealing 804.7055811.3 810.4 808.5 793.4 798.7 808.8 813.6 point Young's 82.61094 84.583.8 83.3 82.5 82.9 83.2 83.5 modulus Etch index 22.0199 17.8746920.00777 21.23817 23.26557 22.86863 21.09331 20.06004 Density 2.6 2.5932.593 2.593 2.579 2.579 2.588 2.597 T (200P) 1706 1709 1701 1695 16621667 1696 1700 T (35kP) 1312 1320 1317 1314 1287 1295 1315 1320 T 11901240 1210 1210 1180 1180 1215 1205 (liquidus) Liquidus 472860.5 178135344750.8 314204.8 368621.5 436103.1 292593.6 422856.3 Viscosity Sample406 407 408 409 410 411 412 413 SiO2 72.05 71.92 71.9 72.09 71.93 70.5272.29 71.75 Al2O3 12.27 12.33 12.37 12.3 12.34 12.97 12.48 12.46 B2O30.49 0.65 0.68 0.51 0.66 2.32 1.02 0.88 MgO 5.06 5.01 4.94 4.98 4.973.65 4.08 4.82 CaO 5.15 5.15 5.19 5.21 5.19 4.95 5.38 5.23 SrO 1.5 1.481.45 1.41 1.44 1.27 2.26 1.41 BaO 3.37 3.34 3.35 3.4 3.35 4.07 2.38 3.32ZnO 0 0 0 0 0 0 0 0 SnO2 0.08 0.09 0.09 0.08 0.09 0.11 0.09 0.1 Fe2O30.01 0.01 0.01 0.01 0.01 0.11 0.01 0.01 ZrO2 0.01 0.01 0.01 0.01 0.010.02 0.01 0.01 RO/Al2O3 1.229014 1.214923 1.206952 1.219512 1.2115071.074788 1.129808 1.186196 Annealing 811.9 811.05 810 812 810.25 793.9815.3 808.1 point Young's 84.1 83.4 83.75 84 83.65 82.1 83.4 83.4modulus Etch index 21.04336 21.11301 21.1736 20.96679 21.09031 24.0338919.89371 21.28791 Density 2.598 2.595 2.5955 2.598 2.5955 2.605 2.593 T(200P) 1699 1698 1698 1699 1697 1678 1704 1697 T (35kP) 1318 1317 13161320 1317 1304 1322 1313 T 1200 1207.5 1205 1200 1205 1180 1235 1210(liquidus) Liquidus 447767.7 363998.3 369457.7 462624.3 380809.7521552.7 305078.8 Viscosity Sample 414 415 416 417 418 419 420 421 SiO272.66 71.73 71.46 70.48 71.92 72.68 70.33 71.1 Al2O3 11.13 12.54 12.5212.58 12.38 11.4 12.53 12.46 B2O3 0.29 0.54 0.51 1.89 0.69 0.19 1.841.89 MgO 6.71 5.02 5.37 4.64 4.9 6.41 4.96 4.32 CaO 3.59 5.07 5.04 5.155.22 4.1 5.1 5.15 SrO 3.02 1.29 1.27 1.23 1.41 2.16 1.22 1.19 BaO 2.493.7 3.71 3.92 3.36 2.95 3.9 3.77 ZnO 0 0 0 0 0 0 0 0 SnO2 0.09 0.09 0.090.09 0.09 0.09 0.09 0.09 Fe2O3 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01ZrO2 0.01 0.01 0.01 0.01 0.01 0.01 0.01 0.01 RO/Al2O3 1.420485 1.2025521.229233 1.187599 1.202746 1.370175 1.211492 1.158106 Annealing 807.4814.3 811.2 794 810.05 811.7 791.5 798.1 point Young's 84.9 83.8 83.8 8283.7 84 82.5 82.3 modulus Etch index 18.29531 22.0506 22.48202 24.150521.12078 18.52005 24.27848 22.49264 Density 2.592 2.608 2.612 2.6042.5955 2.595 2.61 2.591 T (200P) 1705 1689 1685 1678 1698 1708 1668 1688T (35kP) 1316 1313 1305 1296 1316 1320 1288 1301 T 1275 1190 1185 11501205 1270 1140 1150 (liquidus) Liquidus 77925.46 526172.7 493710.8944151.7 375601.8 93163.61 1021322 1051025 Viscosity Sample 422 423 424425 426 SiO2 70.76 71.42 70.93 71.35 71.18 Al2O3 12.45 12.8 12.48 12.4512.96 B2O3 1.91 0.97 1.87 2.56 1.73 MgO 4.66 4.85 4.46 3.52 3.75 CaO5.17 4.85 5.17 5.18 4.8 SrO 1.19 1.63 1.19 1.4 1.19 BaO 3.74 3.38 3.783.42 4.26 ZnO 0 0 0 0 0 SnO2 0.09 0.07 0.09 0.1 0.09 Fe2O3 0.01 0.010.01 0.01 0.01 ZrO2 0.01 0 0.01 0.01 0.01 RO/Al2O3 1.185542 1.1492191.169872 1.085944 1.080247 Annealing 794.4 810.8 798.5 794.1319 805.2point Young's 82.4 83.2 83.3 80.98138 81.4 modulus Etch index 23.0561722.23406 22.87568 21.30132 23.45326 Density 2.596 2.598 2.594 2.607 T(200P) 1682 1695 1678 1696 T (35kP) 1296 1312 1297 1312 T 1150 1250 11501220 (liquidus) Liquidus 929795.4 124647.6 946089.9 238329.1 Viscosity

What is claimed is:
 1. A glass comprising in mole percent on an oxidebasis: SiO₂ 60-80, Al₂O₃ 13.0-14.0, B₂O₃ 0.1-3.0, MgO 0-20, CaO5.25-6.0, SrO 0-20, BaO 0-20, ZnO 0-20; wherein the glass has thefollowing properties: an annealing temperature greater than or equal to785° C.; a density less than or equal to 2.65 g/cc; a T_(200P) less thanor equal to 1750° C.; a T_(35kP) less than or equal to 1340° C.; and aYoung's modulus greater than or equal to 82 GPa; and wherein the glasshas the following compositional characteristics: (i) an etch indexgreater than or equal to 24 as defined by the equation:etchindex=−54.6147+(2.50004)*(Al₂O₃)+(1.3134)*(B₂O₃)+(1.84106)*(MgO)+(3.01223)*(CaO)+(3.7248)*(SrO)+(4.13149)*(BaO),where Al₂O₃, B₂O₃, MgO, CaO, SrO, and BaO are in mole percent; and (ii)the glass is substantially free of alkalis.
 2. The glass of claim 1,wherein the annealing temperature is greater than or equal to 800° C. 3.The glass of claim 1, wherein the density is less than or equal to 2.61g/cc.
 4. The glass of claim 1, wherein the T_(200P) less than or equalto 1700°C.
 5. The glass of claim 1, wherein the T_(35kP) less than orequal to 1310°C.
 6. The glass of claim 1, wherein the glass comprisesMgO, in mole percent on an oxide basis, in the range 1.0-7.2.
 7. Theglass of claim 6, wherein the glass comprises MgO, in mole percent on anoxide basis, in the range 3.1-5.8.
 8. The glass of claim 1, wherein theglass comprises SrO, in mole percent on an oxide basis, in therange >0-4.2.
 9. The glass of claim 8, wherein the glass comprises SrO,in mole percent on an oxide basis, in the range >0-2.0.
 10. The glass ofclaim 1, wherein the glass comprises BaO, in mole percent on an oxidebasis, in the range 1.2-4.4.
 11. The glass of claim 10, wherein theglass comprises BaO, in mole percent on an oxide basis, in the range2.6-4.4.
 12. The glass of claim 1, wherein the glass comprises, in molepercent oil an oxide basis, SiO₂ 68.0-72.0.
 13. The glass of claim 1,wherein the glass comprises SiO₂, in mole percent on an oxide basis, inthe range 68.1-72.3.
 14. An aluminosilicate glass article that issubstantially free of alkalis, wherein the glass article comprises inmole percent on an oxide basis: SiO₂ 60-80, Al₂O₃ 13.0-14.0, B₂O₃0.1-3.0, MgO 0-20, CaO 5.25-6.0, SrO 0-20, BaO 0-20, ZnO 0-20; and hasthe following properties: an annealing temperature greater than or equalto 795° C.; a density less than or equal to 2.63 g/cc; a T_(200P) lessthan or equal to 1730° C.; a T_(35kP) less than or equal to 1320° C.;and a Young's modulus greater than or equal to 81.5 GPa; and wherein theglass article has the following compositional characteristic: an etchindex greater than or equal to 24 as defined by the equation:etchindex=−54.6147+(2.50004)*(Al₂O₃)+(1.3134)*(B₂O₃)+(1.84106)*(MgO)+(3.01223)*(CaO)+(3.7248)*(SrO)+(4.13149)*(BaO),where Al₂O₃, B₂O₃, MgO, CaO, SrO, and BaO are in mole percent.
 15. Analuminosilicate glass article that is substantially free of alkalis,wherein the glass article comprises in mole percent on an oxide basis:SiO₂ 60-80, Al₂O₃ 13.0-14.0, B₂O₃ 0.1-3.0, MgO 0-20, CaO 5.25-6.0, SrO0-20, BaO 0-20, ZnO 0-20; and has the following properties: an annealingtemperature greater than or equal to 800° C.; a density less than orequal to 2.61 g/cc; a T_(200P) less than or equal to 1710° C.; aT_(35kP) less than or equal to 1310° C.; and a Young's modulus greaterthan or equal to 81.2 GPa; and wherein the glass article has thefollowing compositional characteristic: an etch index greater than orequal to 24 as defined by the equation:etchindex=−54.6147+(2.50004)*(Al₂O₃)+(1.3134)*(B₂O₃)+(1.84106)*(MgO)+(3.01223)*(CaO)+(3.7248)*(SrO)+(4.13149)*(BaO),where Al₂O₃, B₂O₃, MgO, CaO, SrO, and BaO are in mole percent.
 16. Aglass substantially free of alkalis comprising in mole % on an oxidebasis: SiO₂ 60-80, Al₂O₃ 13.0-14.0, B₂O₃ 0.1-3.0, MgO 0-20, CaO5.25-6.0, SrO 0-20, BaO 0-20, ZnO 0-20; wherein: (i)(MgO+CaO+SrO+BaO)/Al₂O₃ is in the range of 1.0-1.6, where Al₂O₃, MgO,CaO, SrO, and BaO are in mole percent, (ii) the ratio ofMgO/(MgO+CaO+SrO+BaO) is in the range of 0.22-0.37, where MgO, CaO, SrO,and BaO are in mole percent, (iii) the glass has an etch index greaterthan or equal to 24 as defined by the equation:etchindex=−54.6147+(2.50004)*(Al₂O₃)+(1.3134)*(B₂O₃)+(1.84106)*(MgO)+(3.01223)*(CaO)+(3.7248)*(SrO)+(4.13149)*(BaO), where Al₂O₃, B₂O₃, MgO, CaO, SrO, and BaO are in mole percent, and (iv)the glass has the following properties: T(ann)>785° C., density <2.65g/cc, T(200P)<1750° C., T(35kP)<1340° C., and Young's modulus >82 GPa.